Move Extension into extensions namespace

BUG=117262
TBR=aa@chromium.org

Review URL: https://chromiumcodereview.appspot.com/10375021

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@138074 0039d316-1c4b-4281-b951-d872f2087c98

459 files changed, 1644 insertions, 963 deletions

diff --git a/chrome/browser/app_controller_mac.mm b/chrome/browser/app_controller_mac.mm
index e3ae37c..4631613 100644
--- a/chrome/browser/app_controller_mac.mm
+++ b/chrome/browser/app_controller_mac.mm
@@ -925,7 +925,7 @@ const AEEventClass kAECloudPrintUninstallClass = 'GCPu';
   BackgroundApplicationListModel applications(profile);
   DCHECK(tag >= 0 &&
          tag < static_cast<int>(applications.size()));
-  const Extension* extension = applications.GetExtension(tag);
+  const extensions::Extension* extension = applications.GetExtension(tag);
   BackgroundModeManager::LaunchBackgroundApplication(profile, extension);
 }
 
@@ -1239,7 +1239,8 @@ const AEEventClass kAECloudPrintUninstallClass = 'GCPu';
       NSString* menuStr =
           l10n_util::GetNSStringWithFixup(IDS_BACKGROUND_APPS_MAC);
       scoped_nsobject<NSMenu> appMenu([[NSMenu alloc] initWithTitle:menuStr]);
-      for (ExtensionList::const_iterator cursor = applications.begin();
+      for (extensions::ExtensionList::const_iterator cursor =
+            applications.begin();
            cursor != applications.end();
            ++cursor, ++position) {
         DCHECK_EQ(applications.GetPosition(*cursor), position);
diff --git a/chrome/browser/autocomplete/keyword_provider.cc b/chrome/browser/autocomplete/keyword_provider.cc
index 1f70105..ba2028b 100644
--- a/chrome/browser/autocomplete/keyword_provider.cc
+++ b/chrome/browser/autocomplete/keyword_provider.cc
@@ -172,7 +172,7 @@ string16 KeywordProvider::GetKeywordForText(
 
   // Don't provide a keyword for inactive/disabled extension keywords.
   if (template_url->IsExtensionKeyword()) {
-    const Extension* extension = profile_->GetExtensionService()->
+    const extensions::Extension* extension = profile_->GetExtensionService()->
         GetExtensionById(template_url->GetExtensionId(), false);
     if (!extension ||
         (profile_->IsOffTheRecord() &&
@@ -249,7 +249,7 @@ void KeywordProvider::Start(const AutocompleteInput& input,
     // we're incognito), or disabled.
     if (profile_ && template_url->IsExtensionKeyword()) {
       ExtensionService* service = profile_->GetExtensionService();
-      const Extension* extension = service->GetExtensionById(
+      const extensions::Extension* extension = service->GetExtensionById(
           template_url->GetExtensionId(), false);
       bool enabled =
           extension && (!profile_->IsOffTheRecord() ||
diff --git a/chrome/browser/automation/automation_provider_json.cc b/chrome/browser/automation/automation_provider_json.cc
index 2350ed3..6b27e46 100644
--- a/chrome/browser/automation/automation_provider_json.cc
+++ b/chrome/browser/automation/automation_provider_json.cc
@@ -14,6 +14,7 @@
 #include "chrome/browser/profiles/profile.h"
 #include "chrome/common/automation_id.h"
 #include "chrome/common/automation_messages.h"
+#include "chrome/common/extensions/extension.h"
 #include "content/public/browser/web_contents.h"
 
 using automation::Error;
@@ -181,7 +182,7 @@ bool GetExtensionFromJSONArgsHelper(
     const std::string& key,
     Profile* profile,
     bool include_disabled,
-    const Extension** extension,
+    const extensions::Extension** extension,
     std::string* error) {
   std::string id;
   if (!args->GetString(key, &id)) {
@@ -200,7 +201,7 @@ bool GetExtensionFromJSONArgsHelper(
                                 id.c_str());
     return false;
   }
-  const Extension* installed_extension =
+  const extensions::Extension* installed_extension =
       service->GetExtensionById(id, include_disabled);
   if (!installed_extension) {
     *error = "Extension is disabled or has crashed.";
@@ -216,7 +217,7 @@ bool GetExtensionFromJSONArgs(
     base::DictionaryValue* args,
     const std::string& key,
     Profile* profile,
-    const Extension** extension,
+    const extensions::Extension** extension,
     std::string* error) {
   return GetExtensionFromJSONArgsHelper(
       args, key, profile, true /* include_disabled */, extension, error);
@@ -226,7 +227,7 @@ bool GetEnabledExtensionFromJSONArgs(
     base::DictionaryValue* args,
     const std::string& key,
     Profile* profile,
-    const Extension** extension,
+    const extensions::Extension** extension,
     std::string* error) {
   return GetExtensionFromJSONArgsHelper(
       args, key, profile, false /* include_disabled */, extension, error);
diff --git a/chrome/browser/automation/automation_provider_json.h b/chrome/browser/automation/automation_provider_json.h
index d2ced1b..34680a5 100644
--- a/chrome/browser/automation/automation_provider_json.h
+++ b/chrome/browser/automation/automation_provider_json.h
@@ -16,7 +16,6 @@
 class AutomationId;
 class AutomationProvider;
 class Browser;
-class Extension;
 class Profile;
 
 namespace base {
@@ -29,6 +28,10 @@ class RenderViewHost;
 class WebContents;
 }
 
+namespace extensions {
+class Extension;
+}
+
 namespace IPC {
 class Message;
 }
@@ -114,7 +117,7 @@ bool GetExtensionFromJSONArgs(
     base::DictionaryValue* args,
     const std::string& key,
     Profile* profile,
-    const Extension** extension,
+    const extensions::Extension** extension,
     std::string* error) WARN_UNUSED_RESULT;
 
 // Gets the enabled extension specified by the given dictionary |args|. |args|
@@ -125,7 +128,7 @@ bool GetEnabledExtensionFromJSONArgs(
     base::DictionaryValue* args,
     const std::string& key,
     Profile* profile,
-    const Extension** extension,
+    const extensions::Extension** extension,
     std::string* error) WARN_UNUSED_RESULT;
 
 #endif  // CHROME_BROWSER_AUTOMATION_AUTOMATION_PROVIDER_JSON_H_
diff --git a/chrome/browser/automation/automation_provider_observers.cc b/chrome/browser/automation/automation_provider_observers.cc
index 339e575..700311b 100644
--- a/chrome/browser/automation/automation_provider_observers.cc
+++ b/chrome/browser/automation/automation_provider_observers.cc
@@ -555,7 +555,8 @@ void ExtensionUninstallObserver::Observe(
     }
 
     case chrome::NOTIFICATION_EXTENSION_UNINSTALL_NOT_ALLOWED: {
-      const Extension* extension = content::Details<Extension>(details).ptr();
+      const extensions::Extension* extension =
+          content::Details<extensions::Extension>(details).ptr();
       if (id_ == extension->id()) {
         scoped_ptr<DictionaryValue> return_value(new DictionaryValue);
         return_value->SetBoolean("success", false);
@@ -615,11 +616,12 @@ void ExtensionReadyNotificationObserver::Observe(
         return;
       break;
     case chrome::NOTIFICATION_EXTENSION_LOADED: {
-      const Extension* loaded_extension =
-          content::Details<const Extension>(details).ptr();
+      const extensions::Extension* loaded_extension =
+          content::Details<const extensions::Extension>(details).ptr();
       // Only track an internal or unpacked extension load.
-      Extension::Location location = loaded_extension->location();
-      if (location != Extension::INTERNAL && location != Extension::LOAD)
+      extensions::Extension::Location location = loaded_extension->location();
+      if (location != extensions::Extension::INTERNAL &&
+          location != extensions::Extension::LOAD)
         return;
       extension_ = loaded_extension;
       if (!DidExtensionViewsStopLoading(manager_))
@@ -731,7 +733,8 @@ void ExtensionsUpdatedObserver::Observe(
       // An extension has either completed update installation and is now
       // loaded, or else the install has been skipped because it is
       // either not allowed or else has been disabled.
-      const Extension* extension = content::Details<Extension>(details).ptr();
+      const extensions::Extension* extension =
+          content::Details<extensions::Extension>(details).ptr();
       in_progress_updates_.erase(extension->id());
       break;
     }
@@ -1876,7 +1879,7 @@ std::vector<DictionaryValue*>* GetAppInfoFromExtensions(
       DictionaryValue* app_info = new DictionaryValue();
       AppLauncherHandler::CreateAppInfo(*ext, NULL, ext_service, app_info);
       app_info->SetBoolean("is_component_extension",
-                           (*ext)->location() == Extension::COMPONENT);
+          (*ext)->location() == extensions::Extension::COMPONENT);
 
       // Convert the launch_type integer into a more descriptive string.
       int launch_type;
diff --git a/chrome/browser/automation/automation_provider_observers.h b/chrome/browser/automation/automation_provider_observers.h
index d8e0d56..0e88d83 100644
--- a/chrome/browser/automation/automation_provider_observers.h
+++ b/chrome/browser/automation/automation_provider_observers.h
@@ -56,7 +56,6 @@
 class AutomationProvider;
 class BalloonCollection;
 class Browser;
-class Extension;
 class ExtensionProcessManager;
 class ExtensionService;
 class InfoBarTabHelper;
@@ -81,6 +80,10 @@ class RenderViewHost;
 class WebContents;
 }
 
+namespace extensions {
+class Extension;
+}
+
 namespace history {
 class TopSites;
 }
@@ -364,7 +367,7 @@ class ExtensionReadyNotificationObserver
   ExtensionService* service_;
   base::WeakPtr<AutomationProvider> automation_;
   scoped_ptr<IPC::Message> reply_message_;
-  const Extension* extension_;
+  const extensions::Extension* extension_;
 
   DISALLOW_COPY_AND_ASSIGN(ExtensionReadyNotificationObserver);
 };
diff --git a/chrome/browser/automation/automation_util.cc b/chrome/browser/automation/automation_util.cc
index f1ea241..12bf075 100644
--- a/chrome/browser/automation/automation_util.cc
+++ b/chrome/browser/automation/automation_util.cc
@@ -438,7 +438,7 @@ AutomationId GetIdForExtensionView(
   return AutomationId(type, id);
 }
 
-AutomationId GetIdForExtension(const Extension* extension) {
+AutomationId GetIdForExtension(const extensions::Extension* extension) {
   return AutomationId(AutomationId::kTypeExtension, extension->id());
 }
 
@@ -526,11 +526,11 @@ bool GetRenderViewForId(
 bool GetExtensionForId(
     const AutomationId& id,
     Profile* profile,
-    const Extension** extension) {
+    const extensions::Extension** extension) {
   if (id.type() != AutomationId::kTypeExtension)
     return false;
   ExtensionService* service = profile->GetExtensionService();
-  const Extension* installed_extension =
+  const extensions::Extension* installed_extension =
       service->GetInstalledExtension(id.id());
   if (installed_extension)
     *extension = installed_extension;
@@ -550,7 +550,7 @@ bool DoesObjectWithIdExist(const AutomationId& id, Profile* profile) {
       return GetExtensionRenderViewForId(id, profile, &rvh);
     }
     case AutomationId::kTypeExtension: {
-      const Extension* extension;
+      const extensions::Extension* extension;
       return GetExtensionForId(id, profile, &extension);
     }
     default:
diff --git a/chrome/browser/automation/automation_util.h b/chrome/browser/automation/automation_util.h
index c33fd72..942a08b 100644
--- a/chrome/browser/automation/automation_util.h
+++ b/chrome/browser/automation/automation_util.h
@@ -13,7 +13,6 @@
 class AutomationId;
 class AutomationProvider;
 class Browser;
-class Extension;
 class GURL;
 class Profile;
 class TabContentsWrapper;
@@ -27,6 +26,10 @@ namespace base {
 class DictionaryValue;
 }
 
+namespace extensions {
+class Extension;
+}
+
 namespace IPC {
 class Message;
 }
@@ -96,7 +99,7 @@ AutomationId GetIdForExtensionView(
     const content::RenderViewHost* render_view_host);
 
 // Returns a valid automation ID for the extension.
-AutomationId GetIdForExtension(const Extension* extension);
+AutomationId GetIdForExtension(const extensions::Extension* extension);
 
 // Gets the tab for the given ID. Returns true on success.
 bool GetTabForId(const AutomationId& id, content::WebContents** tab);
@@ -109,7 +112,7 @@ bool GetRenderViewForId(const AutomationId& id,
 // Gets the extension for the given ID. Returns true on success.
 bool GetExtensionForId(const AutomationId& id,
                        Profile* profile,
-                       const Extension** extension);
+                       const extensions::Extension** extension);
 
 // Returns whether the given ID refers to an actual automation entity.
 bool DoesObjectWithIdExist(const AutomationId& id, Profile* profile);
diff --git a/chrome/browser/automation/testing_automation_provider.cc b/chrome/browser/automation/testing_automation_provider.cc
index 073d986..8480c30 100644
--- a/chrome/browser/automation/testing_automation_provider.cc
+++ b/chrome/browser/automation/testing_automation_provider.cc
@@ -187,6 +187,8 @@ using content::Referrer;
 using content::RenderViewHost;
 using content::SSLStatus;
 using content::WebContents;
+using extensions::Extension;
+using extensions::ExtensionList;
 
 namespace {
 
@@ -3998,9 +4000,8 @@ ListValue* GetAPIPermissions(const Extension* ext) {
 // Sample json input: { "command": "GetExtensionsInfo" }
 // See GetExtensionsInfo() in chrome/test/pyautolib/pyauto.py for sample json
 // output.
-void TestingAutomationProvider::GetExtensionsInfo(
-    DictionaryValue* args,
-    IPC::Message* reply_message) {
+void TestingAutomationProvider::GetExtensionsInfo(DictionaryValue* args,
+                                                  IPC::Message* reply_message) {
   AutomationJSONReply reply(this, reply_message);
   Browser* browser;
   std::string error_msg;
@@ -4046,9 +4047,11 @@ void TestingAutomationProvider::GetExtensionsInfo(
     Extension::Location location = extension->location();
     extension_value->SetBoolean("is_component",
                                 location == Extension::COMPONENT);
-    extension_value->SetBoolean("is_internal", location == Extension::INTERNAL);
+    extension_value->SetBoolean("is_internal",
+                                location == Extension::INTERNAL);
     extension_value->SetBoolean("is_user_installed",
-        location == Extension::INTERNAL || location == Extension::LOAD);
+        location == Extension::INTERNAL ||
+        location == Extension::LOAD);
     extension_value->SetBoolean("is_enabled", service->IsExtensionEnabled(id));
     extension_value->SetBoolean("allowed_in_incognito",
                                 service->IsIncognitoEnabled(id));
@@ -4151,7 +4154,8 @@ void TestingAutomationProvider::SetExtensionStateById(
       AutomationJSONReply(this, reply_message).SendSuccess(NULL);
     }
   } else {
-    service->DisableExtension(extension->id(), Extension::DISABLE_USER_ACTION);
+    service->DisableExtension(extension->id(),
+                              Extension::DISABLE_USER_ACTION);
     AutomationJSONReply(this, reply_message).SendSuccess(NULL);
   }
 
diff --git a/chrome/browser/background/background_application_list_model.cc b/chrome/browser/background/background_application_list_model.cc
index a414cf1..6965c6b 100644
--- a/chrome/browser/background/background_application_list_model.cc
+++ b/chrome/browser/background/background_application_list_model.cc
@@ -27,6 +27,11 @@
 #include "ui/base/l10n/l10n_util_collator.h"
 #include "ui/gfx/image/image.h"
 
+using extensions::Extension;
+using extensions::ExtensionList;
+using extensions::UnloadedExtensionInfo;
+using extensions::UpdatedExtensionPermissionsInfo;
+
 class ExtensionNameComparator {
  public:
   explicit ExtensionNameComparator(icu::Collator* collator);
@@ -228,7 +233,8 @@ BackgroundApplicationListModel::FindApplication(
 }
 
 BackgroundApplicationListModel::Application*
-BackgroundApplicationListModel::FindApplication(const Extension* extension) {
+BackgroundApplicationListModel::FindApplication(
+    const Extension* extension) {
   const std::string& id = extension->id();
   ApplicationMap::iterator found = applications_.find(id);
   return (found == applications_.end()) ? NULL : found->second;
diff --git a/chrome/browser/background/background_application_list_model.h b/chrome/browser/background/background_application_list_model.h
index 8722bc8a..c4f6a45 100644
--- a/chrome/browser/background/background_application_list_model.h
+++ b/chrome/browser/background/background_application_list_model.h
@@ -31,8 +31,9 @@ class BackgroundApplicationListModel : public content::NotificationObserver {
    public:
     // Invoked when data that the model associates with the extension, such as
     // the Icon, has changed.
-    virtual void OnApplicationDataChanged(const Extension* extension,
-                                          Profile* profile);
+    virtual void OnApplicationDataChanged(
+        const extensions::Extension* extension,
+        Profile* profile);
 
     // Invoked when the model detects a previously unknown extension and/or when
     // it no longer detects a previously known extension.
@@ -58,26 +59,26 @@ class BackgroundApplicationListModel : public content::NotificationObserver {
   //       releasing it if the associated background application is unloaded.
   // NOTE: All icons are currently sized as
   //       ExtensionIconSet::EXTENSION_ICON_BITTY.
-  const SkBitmap* GetIcon(const Extension* extension);
+  const SkBitmap* GetIcon(const extensions::Extension* extension);
 
   // Return the position of |extension| within this list model.
-  int GetPosition(const Extension* extension) const;
+  int GetPosition(const extensions::Extension* extension) const;
 
   // Return the extension at the specified |position| in this list model.
-  const Extension* GetExtension(int position) const;
+  const extensions::Extension* GetExtension(int position) const;
 
   // Returns true if the passed extension is a background app.
-  static bool IsBackgroundApp(const Extension& extension,
+  static bool IsBackgroundApp(const extensions::Extension& extension,
                               Profile* profile);
 
   // Dissociate observer from this model.
   void RemoveObserver(Observer* observer);
 
-  ExtensionList::const_iterator begin() const {
+  extensions::ExtensionList::const_iterator begin() const {
     return extensions_.begin();
   }
 
-  ExtensionList::const_iterator end() const {
+  extensions::ExtensionList::const_iterator end() const {
     return extensions_.end();
   }
 
@@ -94,16 +95,17 @@ class BackgroundApplicationListModel : public content::NotificationObserver {
   typedef std::map<std::string, Application*> ApplicationMap;
 
   // Identifies and caches data related to the extension.
-  void AssociateApplicationData(const Extension* extension);
+  void AssociateApplicationData(const extensions::Extension* extension);
 
   // Clears cached data related to |extension|.
-  void DissociateApplicationData(const Extension* extension);
+  void DissociateApplicationData(const extensions::Extension* extension);
 
   // Returns the Application associated with |extension| or NULL.
-  const Application* FindApplication(const Extension* extension) const;
+  const Application* FindApplication(
+      const extensions::Extension* extension) const;
 
   // Returns the Application associated with |extension| or NULL.
-  Application* FindApplication(const Extension* extension);
+  Application* FindApplication(const extensions::Extension* extension);
 
   // content::NotificationObserver implementation.
   virtual void Observe(int type,
@@ -112,29 +114,30 @@ class BackgroundApplicationListModel : public content::NotificationObserver {
 
   // Notifies observers that some of the data associated with this background
   // application, e. g. the Icon, has changed.
-  void SendApplicationDataChangedNotifications(const Extension* extension);
+  void SendApplicationDataChangedNotifications(
+      const extensions::Extension* extension);
 
   // Notifies observers that at least one background application has been added
   // or removed.
   void SendApplicationListChangedNotifications();
 
   // Invoked by Observe for NOTIFICATION_EXTENSION_LOADED.
-  void OnExtensionLoaded(const Extension* extension);
+  void OnExtensionLoaded(const extensions::Extension* extension);
 
   // Invoked by Observe for NOTIFICATION_EXTENSION_UNLOADED.
-  void OnExtensionUnloaded(const Extension* extension);
+  void OnExtensionUnloaded(const extensions::Extension* extension);
 
   // Invoked by Observe for NOTIFICATION_EXTENSION_PERMISSIONS_UPDATED.
   void OnExtensionPermissionsUpdated(
-      const Extension* extension,
-      UpdatedExtensionPermissionsInfo::Reason reason,
+      const extensions::Extension* extension,
+      extensions::UpdatedExtensionPermissionsInfo::Reason reason,
       const ExtensionPermissionSet* permissions);
 
   // Refresh the list of background applications and generate notifications.
   void Update();
 
   ApplicationMap applications_;
-  ExtensionList extensions_;
+  extensions::ExtensionList extensions_;
   ObserverList<Observer> observers_;
   Profile* profile_;
   content::NotificationRegistrar registrar_;
diff --git a/chrome/browser/background/background_application_list_model_unittest.cc b/chrome/browser/background/background_application_list_model_unittest.cc
index fea9d20..982badf 100644
--- a/chrome/browser/background/background_application_list_model_unittest.cc
+++ b/chrome/browser/background/background_application_list_model_unittest.cc
@@ -30,6 +30,8 @@
 // operations to produce a repeatable sequence.
 #define RANDOM_SEED (0x33F7A7A7)
 
+using extensions::Extension;
+
 // For ExtensionService interface when it requires a path that is not used.
 FilePath bogus_file_path() {
   return FilePath(FILE_PATH_LITERAL("//foobar_nonexistent"));
diff --git a/chrome/browser/background/background_contents_service.cc b/chrome/browser/background/background_contents_service.cc
index 3cfaeab..909ef7a 100644
--- a/chrome/browser/background/background_contents_service.cc
+++ b/chrome/browser/background/background_contents_service.cc
@@ -37,6 +37,8 @@
 
 using content::SiteInstance;
 using content::WebContents;
+using extensions::Extension;
+using extensions::UnloadedExtensionInfo;
 
 namespace {
 
@@ -55,7 +57,8 @@ void ScheduleCloseBalloon(const std::string& extension_id) {
 
 class CrashNotificationDelegate : public NotificationDelegate {
  public:
-  CrashNotificationDelegate(Profile* profile, const Extension* extension)
+  CrashNotificationDelegate(Profile* profile,
+                            const Extension* extension)
       : profile_(profile),
         is_hosted_app_(extension->is_hosted_app()),
         extension_id_(extension->id()) {
@@ -366,8 +369,8 @@ void BackgroundContentsService::LoadBackgroundContentsFromPrefs(
   for (DictionaryValue::key_iterator it = contents->begin_keys();
        it != contents->end_keys(); ++it) {
     // Check to make sure that the parent extension is still enabled.
-    const Extension* extension = extensions_service->GetExtensionById(
-        *it, false);
+    const Extension* extension = extensions_service->
+        GetExtensionById(*it, false);
     if (!extension) {
       // We should never reach here - it should not be possible for an app
       // to become uninstalled without the associated BackgroundContents being
diff --git a/chrome/browser/background/background_mode_manager.cc b/chrome/browser/background/background_mode_manager.cc
index 8d7a288..69bd254 100644
--- a/chrome/browser/background/background_mode_manager.cc
+++ b/chrome/browser/background/background_mode_manager.cc
@@ -42,6 +42,8 @@
 #include "ui/base/resource/resource_bundle.h"
 
 using content::UserMetricsAction;
+using extensions::Extension;
+using extensions::UpdatedExtensionPermissionsInfo;
 
 BackgroundModeManager::BackgroundModeData::BackgroundModeData(
     int command_id,
@@ -80,7 +82,8 @@ void BackgroundModeManager::BackgroundModeData::ExecuteCommand(int item) {
       break;
     default:
       // Launch the app associated with this item.
-      const Extension* extension = applications_->GetExtension(item);
+      const Extension* extension = applications_->
+          GetExtension(item);
       BackgroundModeManager::LaunchBackgroundApplication(profile_, extension);
       break;
   }
@@ -109,7 +112,8 @@ void BackgroundModeManager::BackgroundModeData::BuildProfileMenu(
     menu->AddItemWithStringId(IDC_MinimumLabelValue,
                               IDS_BACKGROUND_APP_NOT_INSTALLED);
   } else {
-    for (ExtensionList::const_iterator cursor = applications_->begin();
+    for (extensions::ExtensionList::const_iterator cursor =
+             applications_->begin();
          cursor != applications_->end();
          ++cursor, ++position) {
       const SkBitmap* icon = applications_->GetIcon(*cursor);
diff --git a/chrome/browser/background/background_mode_manager.h b/chrome/browser/background/background_mode_manager.h
index c972048..be5f5fe 100644
--- a/chrome/browser/background/background_mode_manager.h
+++ b/chrome/browser/background/background_mode_manager.h
@@ -20,13 +20,16 @@
 
 class Browser;
 class CommandLine;
-class Extension;
 class PrefService;
 class Profile;
 class ProfileInfoCache;
 class StatusIcon;
 class StatusTray;
 
+namespace extensions {
+class Extension;
+}
+
 // BackgroundModeManager is responsible for switching Chrome into and out of
 // "background mode" and for providing UI for the user to exit Chrome when there
 // are no open browser windows.
@@ -56,7 +59,7 @@ class BackgroundModeManager
   virtual void RegisterProfile(Profile* profile);
 
   static void LaunchBackgroundApplication(Profile* profile,
-                                          const Extension* extension);
+      const extensions::Extension* extension);
 
   // For testing purposes.
   int NumberOfBackgroundModeData();
@@ -153,7 +156,7 @@ class BackgroundModeManager
                        const content::NotificationDetails& details) OVERRIDE;
 
   // BackgroundApplicationListModel::Observer implementation.
-  virtual void OnApplicationDataChanged(const Extension* extension,
+  virtual void OnApplicationDataChanged(const extensions::Extension* extension,
                                         Profile* profile) OVERRIDE;
   virtual void OnApplicationListChanged(Profile* profile) OVERRIDE;
 
@@ -177,7 +180,7 @@ class BackgroundModeManager
   // Invoked when an extension is installed so we can ensure that
   // launch-on-startup is enabled if appropriate. |extension| can be NULL when
   // called from unit tests.
-  void OnBackgroundAppInstalled(const Extension* extension);
+  void OnBackgroundAppInstalled(const extensions::Extension* extension);
 
   // Called to make sure that our launch-on-startup mode is properly set.
   // (virtual so we can override for tests).
@@ -185,7 +188,7 @@ class BackgroundModeManager
 
   // Invoked when a background app is installed so we can display a
   // platform-specific notification to the user.
-  void DisplayAppInstalledNotification(const Extension* extension);
+  void DisplayAppInstalledNotification(const extensions::Extension* extension);
 
   // Invoked to put Chrome in KeepAlive mode - chrome runs in the background
   // and has a status bar icon.
diff --git a/chrome/browser/background/background_mode_manager_aura.cc b/chrome/browser/background/background_mode_manager_aura.cc
index 223c8ea..d66b6a4 100644
--- a/chrome/browser/background/background_mode_manager_aura.cc
+++ b/chrome/browser/background/background_mode_manager_aura.cc
@@ -4,6 +4,7 @@
 
 #include "chrome/browser/background/background_mode_manager.h"
 
+#include "chrome/common/extensions/extension.h"
 #include "grit/generated_resources.h"
 #include "ui/base/l10n/l10n_util.h"
 
@@ -14,7 +15,7 @@ void BackgroundModeManager::EnableLaunchOnStartup(bool should_launch) {
 }
 
 void BackgroundModeManager::DisplayAppInstalledNotification(
-    const Extension* extension) {
+    const extensions::Extension* extension) {
   NOTIMPLEMENTED();
 }
 
diff --git a/chrome/browser/background/background_mode_manager_chromeos.cc b/chrome/browser/background/background_mode_manager_chromeos.cc
index cee80ae..a5be498 100644
--- a/chrome/browser/background/background_mode_manager_chromeos.cc
+++ b/chrome/browser/background/background_mode_manager_chromeos.cc
@@ -4,6 +4,7 @@
 
 #include "chrome/browser/background/background_mode_manager.h"
 
+#include "chrome/common/extensions/extension.h"
 #include "grit/generated_resources.h"
 #include "ui/base/l10n/l10n_util.h"
 
@@ -12,7 +13,7 @@ void BackgroundModeManager::EnableLaunchOnStartup(bool should_launch) {
 }
 
 void BackgroundModeManager::DisplayAppInstalledNotification(
-    const Extension* extension) {
+    const extensions::Extension* extension) {
   // No need to display anything on ChromeOS because all extensions run all
   // the time anyway.
 }
diff --git a/chrome/browser/background/background_mode_manager_gtk.cc b/chrome/browser/background/background_mode_manager_gtk.cc
index 890b437..c61a302 100644
--- a/chrome/browser/background/background_mode_manager_gtk.cc
+++ b/chrome/browser/background/background_mode_manager_gtk.cc
@@ -22,6 +22,7 @@
 #include "ui/base/l10n/l10n_util.h"
 
 using content::BrowserThread;
+using extensions::Extension;
 
 namespace {
 
diff --git a/chrome/browser/background/background_mode_manager_mac.mm b/chrome/browser/background/background_mode_manager_mac.mm
index a0e15cc..03c3366 100644
--- a/chrome/browser/background/background_mode_manager_mac.mm
+++ b/chrome/browser/background/background_mode_manager_mac.mm
@@ -74,7 +74,7 @@ void BackgroundModeManager::EnableLaunchOnStartup(bool should_launch) {
 }
 
 void BackgroundModeManager::DisplayAppInstalledNotification(
-    const Extension* extension) {
+    const extensions::Extension* extension) {
   // TODO(atwilson): Display a platform-appropriate notification here.
   // http://crbug.com/74970
 }
diff --git a/chrome/browser/background/background_mode_manager_win.cc b/chrome/browser/background/background_mode_manager_win.cc
index 3322d866..33b79e2 100644
--- a/chrome/browser/background/background_mode_manager_win.cc
+++ b/chrome/browser/background/background_mode_manager_win.cc
@@ -33,7 +33,7 @@ void BackgroundModeManager::EnableLaunchOnStartup(bool should_launch) {
 }
 
 void BackgroundModeManager::DisplayAppInstalledNotification(
-    const Extension* extension) {
+    const extensions::Extension* extension) {
   // Create a status tray notification balloon explaining to the user that
   // a background app has been installed.
   CreateStatusTrayIcon();
diff --git a/chrome/browser/bookmarks/bookmark_extension_api.cc b/chrome/browser/bookmarks/bookmark_extension_api.cc
index 20d7f3a..2543977 100644
--- a/chrome/browser/bookmarks/bookmark_extension_api.cc
+++ b/chrome/browser/bookmarks/bookmark_extension_api.cc
@@ -43,6 +43,7 @@ namespace keys = bookmark_extension_api_constants;
 using base::TimeDelta;
 using content::BrowserThread;
 using content::WebContents;
+
 typedef QuotaLimitHeuristic::Bucket Bucket;
 typedef QuotaLimitHeuristic::Config Config;
 typedef QuotaLimitHeuristic::BucketList BucketList;
@@ -92,7 +93,7 @@ void BookmarksFunction::Run() {
   if (success) {
     content::NotificationService::current()->Notify(
         chrome::NOTIFICATION_EXTENSION_BOOKMARKS_API_INVOKED,
-        content::Source<const Extension>(GetExtension()),
+        content::Source<const extensions::Extension>(GetExtension()),
         content::Details<const BookmarksFunction>(this));
   }
   SendResponse(success);
diff --git a/chrome/browser/chrome_content_browser_client.cc b/chrome/browser/chrome_content_browser_client.cc
index 1c5efe5..c031d11 100644
--- a/chrome/browser/chrome_content_browser_client.cc
+++ b/chrome/browser/chrome_content_browser_client.cc
@@ -153,6 +153,7 @@ using content::QuotaPermissionContext;
 using content::RenderViewHost;
 using content::SiteInstance;
 using content::WebContents;
+using extensions::Extension;
 using webkit_glue::WebPreferences;
 
 namespace {
diff --git a/chrome/browser/chromeos/accessibility/accessibility_util.cc b/chrome/browser/chromeos/accessibility/accessibility_util.cc
index 480ba53..9704d35 100644
--- a/chrome/browser/chromeos/accessibility/accessibility_util.cc
+++ b/chrome/browser/chromeos/accessibility/accessibility_util.cc
@@ -18,6 +18,7 @@
 #include "chrome/browser/profiles/profile.h"
 #include "chrome/browser/profiles/profile_manager.h"
 #include "chrome/browser/speech/extension_api/tts_extension_api_platform.h"
+#include "chrome/common/extensions/extension.h"
 #include "chrome/common/extensions/extension_messages.h"
 #include "chrome/common/extensions/extension_resource.h"
 #include "chrome/common/extensions/user_script.h"
@@ -116,7 +117,7 @@ void EnableSpokenFeedback(bool enabled, content::WebUI* login_web_ui) {
   FilePath path = FilePath(extension_misc::kAccessExtensionPath)
       .AppendASCII(extension_misc::kChromeVoxDirectoryName);
   if (enabled) {  // Load ChromeVox
-    const Extension* extension =
+    const extensions::Extension* extension =
         extension_service->component_loader()->Add(IDR_CHROMEVOX_MANIFEST,
                                                    path);
 
diff --git a/chrome/browser/chromeos/enterprise_extension_observer.cc b/chrome/browser/chromeos/enterprise_extension_observer.cc
index c8e61ef..740fc38 100644
--- a/chrome/browser/chromeos/enterprise_extension_observer.cc
+++ b/chrome/browser/chromeos/enterprise_extension_observer.cc
@@ -34,8 +34,10 @@ void EnterpriseExtensionObserver::Observe(
   if (content::Source<Profile>(source).ptr() != profile_) {
     return;
   }
-  Extension* extension = content::Details<Extension>(details).ptr();
-  if (extension->location() != Extension::EXTERNAL_POLICY_DOWNLOAD) {
+  extensions::Extension* extension =
+      content::Details<extensions::Extension>(details).ptr();
+  if (extension->location() !=
+      extensions::Extension::EXTERNAL_POLICY_DOWNLOAD) {
     return;
   }
   BrowserThread::PostTask(
diff --git a/chrome/browser/chromeos/extensions/external_filesystem_apitest.cc b/chrome/browser/chromeos/extensions/external_filesystem_apitest.cc
index 69ec32d..1ec43c6 100644
--- a/chrome/browser/chromeos/extensions/external_filesystem_apitest.cc
+++ b/chrome/browser/chromeos/extensions/external_filesystem_apitest.cc
@@ -160,10 +160,11 @@ class FileSystemExtensionApiTest : public ExtensionApiTest {
 
   // Loads the extension, which temporarily starts the lazy background page
   // to dispatch the onInstalled event. We wait until it shuts down again.
-  const Extension* LoadExtensionAndWait(const std::string& test_name) {
+  const extensions::Extension* LoadExtensionAndWait(
+      const std::string& test_name) {
     BackgroundObserver page_complete;
     FilePath extdir = test_data_dir_.AppendASCII(test_name);
-    const Extension* extension = LoadExtension(extdir);
+    const extensions::Extension* extension = LoadExtension(extdir);
     if (extension)
       page_complete.WaitUntilClosed();
     return extension;
diff --git a/chrome/browser/chromeos/extensions/file_browser_event_router.cc b/chrome/browser/chromeos/extensions/file_browser_event_router.cc
index ba82050..1bbf6cc 100644
--- a/chrome/browser/chromeos/extensions/file_browser_event_router.cc
+++ b/chrome/browser/chromeos/extensions/file_browser_event_router.cc
@@ -429,7 +429,7 @@ void FileBrowserEventRouter::DispatchFolderChangeEvent(
 
   for (ExtensionUsageRegistry::const_iterator iter = extensions.begin();
        iter != extensions.end(); ++iter) {
-    GURL target_origin_url(Extension::GetBaseURLFromExtensionId(
+    GURL target_origin_url(extensions::Extension::GetBaseURLFromExtensionId(
         iter->first));
     GURL base_url = fileapi::GetFileSystemRootURI(target_origin_url,
         fileapi::kFileSystemTypeExternal);
diff --git a/chrome/browser/chromeos/extensions/file_browser_private_api.cc b/chrome/browser/chromeos/extensions/file_browser_private_api.cc
index b97fa81..674025c 100644
--- a/chrome/browser/chromeos/extensions/file_browser_private_api.cc
+++ b/chrome/browser/chromeos/extensions/file_browser_private_api.cc
@@ -66,6 +66,7 @@ using content::BrowserThread;
 using content::ChildProcessSecurityPolicy;
 using content::SiteInstance;
 using content::WebContents;
+using extensions::Extension;
 using file_handler_util::FileTaskExecutor;
 using gdata::GDataOperationRegistry;
 
diff --git a/chrome/browser/chromeos/extensions/file_handler_util.cc b/chrome/browser/chromeos/extensions/file_handler_util.cc
index 3feb7cb..9802c25 100644
--- a/chrome/browser/chromeos/extensions/file_handler_util.cc
+++ b/chrome/browser/chromeos/extensions/file_handler_util.cc
@@ -39,6 +39,7 @@ using content::BrowserThread;
 using content::ChildProcessSecurityPolicy;
 using content::SiteInstance;
 using content::WebContents;
+using extensions::Extension;
 
 namespace file_handler_util {
 namespace {
diff --git a/chrome/browser/chromeos/extensions/file_handler_util.h b/chrome/browser/chromeos/extensions/file_handler_util.h
index d38cb6b..6ef6760 100644
--- a/chrome/browser/chromeos/extensions/file_handler_util.h
+++ b/chrome/browser/chromeos/extensions/file_handler_util.h
@@ -99,7 +99,7 @@ class FileTaskExecutor : public base::RefCountedThreadSafe<FileTaskExecutor> {
   class ExecuteTasksFileSystemCallbackDispatcher;
   void RequestFileEntryOnFileThread(
       const GURL& handler_base_url,
-      const scoped_refptr<const Extension>& handler,
+      const scoped_refptr<const extensions::Extension>& handler,
       int handler_pid,
       const std::vector<GURL>& file_urls);
 
@@ -118,7 +118,7 @@ class FileTaskExecutor : public base::RefCountedThreadSafe<FileTaskExecutor> {
   // will be given to the handler extension host process.
   void InitHandlerHostFileAccessPermissions(
       const FileDefinitionList& file_list,
-      const Extension* handler_extension,
+      const extensions::Extension* handler_extension,
       const std::string& action_id);
   // Registers file permissions from |handler_host_permissions_| with
   // ChildProcessSecurityPolicy for process with id |handler_pid|.
diff --git a/chrome/browser/chromeos/extensions/file_manager_util.cc b/chrome/browser/chromeos/extensions/file_manager_util.cc
index 38439424..9509d86 100644
--- a/chrome/browser/chromeos/extensions/file_manager_util.cc
+++ b/chrome/browser/chromeos/extensions/file_manager_util.cc
@@ -463,7 +463,7 @@ void OpenFileBrowser(const FilePath& path,
   if (!service)
     return;
 
-  const Extension* extension =
+  const extensions::Extension* extension =
       service->GetExtensionById(kFileBrowserDomain, false);
   if (!extension)
     return;
diff --git a/chrome/browser/chromeos/kiosk_mode/kiosk_mode_screensaver.cc b/chrome/browser/chromeos/kiosk_mode/kiosk_mode_screensaver.cc
index caa1581..4063852 100644
--- a/chrome/browser/chromeos/kiosk_mode/kiosk_mode_screensaver.cc
+++ b/chrome/browser/chromeos/kiosk_mode/kiosk_mode_screensaver.cc
@@ -21,6 +21,8 @@
 #include "content/public/browser/browser_thread.h"
 #include "content/public/browser/notification_service.h"
 
+using extensions::Extension;
+
 namespace chromeos {
 
 typedef base::Callback<void(
diff --git a/chrome/browser/chromeos/kiosk_mode/kiosk_mode_screensaver.h b/chrome/browser/chromeos/kiosk_mode/kiosk_mode_screensaver.h
index 449539f..701c18b 100644
--- a/chrome/browser/chromeos/kiosk_mode/kiosk_mode_screensaver.h
+++ b/chrome/browser/chromeos/kiosk_mode/kiosk_mode_screensaver.h
@@ -13,9 +13,12 @@
 #include "content/public/browser/notification_observer.h"
 #include "content/public/browser/notification_registrar.h"
 
-class Extension;
 class Profile;
 
+namespace extensions {
+class Extension;
+}
+
 namespace chromeos {
 
 class KioskModeScreensaver : public PowerManagerClient::Observer,
@@ -45,7 +48,7 @@ class KioskModeScreensaver : public PowerManagerClient::Observer,
 
   // Called back on the UI thread to Setup the screensaver with the now unpacked
   // and loaded extension.
-  void SetupScreensaver(scoped_refptr<Extension> extension,
+  void SetupScreensaver(scoped_refptr<extensions::Extension> extension,
                         Profile* default_profile,
                         const FilePath& extension_base_path);
 
diff --git a/chrome/browser/chromeos/offline/offline_load_page.cc b/chrome/browser/chromeos/offline/offline_load_page.cc
index ac107da..183c4a2 100644
--- a/chrome/browser/chromeos/offline/offline_load_page.cc
+++ b/chrome/browser/chromeos/offline/offline_load_page.cc
@@ -98,7 +98,7 @@ std::string OfflineLoadPage::GetHTMLContents() {
   Profile* profile = Profile::FromBrowserContext(
       web_contents_->GetBrowserContext());
   DCHECK(profile);
-  const Extension* extension = NULL;
+  const extensions::Extension* extension = NULL;
   ExtensionService* extensions_service = profile->GetExtensionService();
   // Extension service does not exist in test.
   if (extensions_service)
@@ -138,7 +138,7 @@ void OfflineLoadPage::OnDontProceed() {
 }
 
 void OfflineLoadPage::GetAppOfflineStrings(
-    const Extension* app,
+    const extensions::Extension* app,
     const string16& failed_url,
     DictionaryValue* strings) const {
   strings->SetString("title", app->name());
diff --git a/chrome/browser/chromeos/offline/offline_load_page.h b/chrome/browser/chromeos/offline/offline_load_page.h
index 1e5a78f..52fab74 100644
--- a/chrome/browser/chromeos/offline/offline_load_page.h
+++ b/chrome/browser/chromeos/offline/offline_load_page.h
@@ -14,8 +14,6 @@
 #include "googleurl/src/gurl.h"
 #include "net/base/network_change_notifier.h"
 
-class Extension;
-
 namespace base {
 class DictionaryValue;
 }
@@ -25,6 +23,10 @@ class InterstitialPage;
 class WebContents;
 }
 
+namespace extensions {
+class Extension;
+}
+
 namespace chromeos {
 
 // OfflineLoadPage class shows the interstitial page that is shown
@@ -67,7 +69,7 @@ class OfflineLoadPage : public content::InterstitialPageDelegate,
 
   // Retrieves template strings of the offline page for app and
   // normal site.
-  void GetAppOfflineStrings(const Extension* app,
+  void GetAppOfflineStrings(const extensions::Extension* app,
                             const string16& faield_url,
                             base::DictionaryValue* strings) const;
   void GetNormalOfflineStrings(const string16& faield_url,
diff --git a/chrome/browser/component_updater/component_unpacker.cc b/chrome/browser/component_updater/component_unpacker.cc
index a15d13a..ec697ac 100644
--- a/chrome/browser/component_updater/component_unpacker.cc
+++ b/chrome/browser/component_updater/component_unpacker.cc
@@ -20,6 +20,7 @@
 #include "crypto/signature_verifier.h"
 
 using crypto::SecureHash;
+using extensions::Extension;
 
 namespace {
 // This class makes sure that the CRX digital signature is valid
diff --git a/chrome/browser/component_updater/component_updater_service.cc b/chrome/browser/component_updater/component_updater_service.cc
index 99df4d6..33e08ec 100644
--- a/chrome/browser/component_updater/component_updater_service.cc
+++ b/chrome/browser/component_updater/component_updater_service.cc
@@ -37,6 +37,7 @@
 using content::BrowserThread;
 using content::UtilityProcessHost;
 using content::UtilityProcessHostClient;
+using extensions::Extension;
 
 // The component updater is designed to live until process shutdown, so
 // base::Bind() calls are not refcounted.
diff --git a/chrome/browser/content_settings/content_settings_platform_app_provider.cc b/chrome/browser/content_settings/content_settings_platform_app_provider.cc
index 53e0386..f95b470 100644
--- a/chrome/browser/content_settings/content_settings_platform_app_provider.cc
+++ b/chrome/browser/content_settings/content_settings_platform_app_provider.cc
@@ -16,6 +16,8 @@
 #include "content/public/browser/notification_details.h"
 #include "content/public/browser/notification_service.h"
 
+using extensions::UnloadedExtensionInfo;
+
 namespace content_settings {
 
 PlatformAppProvider::PlatformAppProvider(ExtensionService* extension_service)
@@ -64,7 +66,8 @@ void PlatformAppProvider::Observe(int type,
       break;
     }
     case chrome::NOTIFICATION_EXTENSION_LOADED: {
-      const Extension* extension = content::Details<Extension>(details).ptr();
+      const extensions::Extension* extension =
+          content::Details<extensions::Extension>(details).ptr();
       if (extension->plugins().size() > 0)
         SetContentSettingForExtension(extension, CONTENT_SETTING_ALLOW);
       break;
@@ -88,7 +91,7 @@ void PlatformAppProvider::ShutdownOnUIThread() {
 }
 
 void PlatformAppProvider::SetContentSettingForExtension(
-    const Extension* extension,
+    const extensions::Extension* extension,
     ContentSetting setting) {
   scoped_ptr<ContentSettingsPattern::BuilderInterface> pattern_builder(
       ContentSettingsPattern::CreateBuilder(false));
diff --git a/chrome/browser/content_settings/content_settings_platform_app_provider.h b/chrome/browser/content_settings/content_settings_platform_app_provider.h
index 2d93a9e..d481273 100644
--- a/chrome/browser/content_settings/content_settings_platform_app_provider.h
+++ b/chrome/browser/content_settings/content_settings_platform_app_provider.h
@@ -13,9 +13,12 @@
 #include "content/public/browser/notification_observer.h"
 #include "content/public/browser/notification_registrar.h"
 
-class Extension;
 class ExtensionService;
 
+namespace extensions {
+class Extension;
+}
+
 namespace content_settings {
 
 // A content settings provider which disables certain plugins for platform apps.
@@ -49,7 +52,7 @@ class PlatformAppProvider : public ObservableProvider,
                        const content::NotificationSource& source,
                        const content::NotificationDetails& details) OVERRIDE;
  private:
-  void SetContentSettingForExtension(const Extension* extension,
+  void SetContentSettingForExtension(const extensions::Extension* extension,
                                      ContentSetting setting);
 
   OriginIdentifierValueMap value_map_;
diff --git a/chrome/browser/download/chrome_download_manager_delegate.cc b/chrome/browser/download/chrome_download_manager_delegate.cc
index 00580825..aad682d 100644
--- a/chrome/browser/download/chrome_download_manager_delegate.cc
+++ b/chrome/browser/download/chrome_download_manager_delegate.cc
@@ -114,7 +114,7 @@ bool ChromeDownloadManagerDelegate::IsExtensionDownload(
   if (item->PromptUserForSaveLocation())
     return false;
 
-  if (item->GetMimeType() == Extension::kMimeType ||
+  if (item->GetMimeType() == extensions::Extension::kMimeType ||
       UserScript::IsURLUserScript(item->GetURL(), item->GetMimeType())) {
     return true;
   } else {
@@ -212,7 +212,7 @@ bool ChromeDownloadManagerDelegate::ShouldOpenFileBasedOnExtension(
   FilePath::StringType extension = path.Extension();
   if (extension.empty())
     return false;
-  if (Extension::IsExtension(path))
+  if (extensions::Extension::IsExtension(path))
     return false;
   DCHECK(extension[0] == FilePath::kExtensionSeparator);
   extension.erase(0, 1);
diff --git a/chrome/browser/download/download_browsertest.cc b/chrome/browser/download/download_browsertest.cc
index d6e2d5b..097c951 100644
--- a/chrome/browser/download/download_browsertest.cc
+++ b/chrome/browser/download/download_browsertest.cc
@@ -70,6 +70,7 @@ using content::DownloadManager;
 using content::DownloadPersistentStoreInfo;
 using content::DownloadUrlParameters;
 using content::WebContents;
+using extensions::Extension;
 
 namespace {
 
diff --git a/chrome/browser/download/download_shelf_context_menu.cc b/chrome/browser/download/download_shelf_context_menu.cc
index 952bc7d..991479e 100644
--- a/chrome/browser/download/download_shelf_context_menu.cc
+++ b/chrome/browser/download/download_shelf_context_menu.cc
@@ -18,6 +18,7 @@
 #include "ui/base/l10n/l10n_util.h"
 
 using content::DownloadItem;
+using extensions::Extension;
 
 DownloadShelfContextMenu::~DownloadShelfContextMenu() {}
 
diff --git a/chrome/browser/extensions/alert_apitest.cc b/chrome/browser/extensions/alert_apitest.cc
index d9388bf..c2b8fc3 100644
--- a/chrome/browser/extensions/alert_apitest.cc
+++ b/chrome/browser/extensions/alert_apitest.cc
@@ -16,7 +16,7 @@
 IN_PROC_BROWSER_TEST_F(ExtensionApiTest, AlertBasic) {
   ASSERT_TRUE(RunExtensionTest("alert")) << message_;
 
-  const Extension* extension = GetSingleLoadedExtension();
+  const extensions::Extension* extension = GetSingleLoadedExtension();
   ExtensionHost* host = browser()->profile()->GetExtensionProcessManager()->
       GetBackgroundHostForExtension(extension->id());
   ASSERT_TRUE(host);
diff --git a/chrome/browser/extensions/all_urls_apitest.cc b/chrome/browser/extensions/all_urls_apitest.cc
index cf353ce..e22e8ec 100644
--- a/chrome/browser/extensions/all_urls_apitest.cc
+++ b/chrome/browser/extensions/all_urls_apitest.cc
@@ -23,10 +23,10 @@ IN_PROC_BROWSER_TEST_F(AllUrlsApiTest, WhitelistedExtension) {
                                           .AppendASCII("execute_script");
 
   // Then add the two extensions to the whitelist.
-  Extension::ScriptingWhitelist whitelist;
-  whitelist.push_back(Extension::GenerateIdForPath(extension_dir1));
-  whitelist.push_back(Extension::GenerateIdForPath(extension_dir2));
-  Extension::SetScriptingWhitelist(whitelist);
+  extensions::Extension::ScriptingWhitelist whitelist;
+  whitelist.push_back(extensions::Extension::GenerateIdForPath(extension_dir1));
+  whitelist.push_back(extensions::Extension::GenerateIdForPath(extension_dir2));
+  extensions::Extension::SetScriptingWhitelist(whitelist);
 
   // Then load extensions.
   ExtensionService* service = browser()->profile()->GetExtensionService();
diff --git a/chrome/browser/extensions/api/alarms/alarms_api_unittest.cc b/chrome/browser/extensions/api/alarms/alarms_api_unittest.cc
index 4103fb5..33c2592 100644
--- a/chrome/browser/extensions/api/alarms/alarms_api_unittest.cc
+++ b/chrome/browser/extensions/api/alarms/alarms_api_unittest.cc
@@ -49,7 +49,8 @@ class ExtensionAlarmsTest : public BrowserWithTestWindowTest {
     alarm_delegate_ = new AlarmDelegate();
     alarm_manager_->set_delegate(alarm_delegate_);
 
-    extension_ = utils::CreateEmptyExtensionWithLocation(Extension::LOAD);
+    extension_ = utils::CreateEmptyExtensionWithLocation(
+        extensions::Extension::LOAD);
   }
 
   base::Value* RunFunctionWithExtension(
@@ -117,7 +118,7 @@ class ExtensionAlarmsTest : public BrowserWithTestWindowTest {
  protected:
   AlarmManager* alarm_manager_;
   AlarmDelegate* alarm_delegate_;
-  scoped_refptr<Extension> extension_;
+  scoped_refptr<extensions::Extension> extension_;
 };
 
 TEST_F(ExtensionAlarmsTest, Create) {
diff --git a/chrome/browser/extensions/api/app/app_api.h b/chrome/browser/extensions/api/app/app_api.h
index 864dece..306c158 100644
--- a/chrome/browser/extensions/api/app/app_api.h
+++ b/chrome/browser/extensions/api/app/app_api.h
@@ -8,11 +8,12 @@
 
 #include "chrome/browser/extensions/extension_function.h"
 
-class Extension;
 class Profile;
 
 namespace extensions {
 
+class Extension;
+
 class AppNotifyFunction : public SyncExtensionFunction {
  public:
   DECLARE_EXTENSION_FUNCTION_NAME("experimental.app.notify");
diff --git a/chrome/browser/extensions/api/commands/extension_command_service.cc b/chrome/browser/extensions/api/commands/extension_command_service.cc
index 593e4b5..949ed96 100644
--- a/chrome/browser/extensions/api/commands/extension_command_service.cc
+++ b/chrome/browser/extensions/api/commands/extension_command_service.cc
@@ -14,6 +14,8 @@
 #include "chrome/common/pref_names.h"
 #include "content/public/browser/notification_service.h"
 
+using extensions::Extension;
+
 namespace {
 
 const char kExtension[] = "extension";
diff --git a/chrome/browser/extensions/api/commands/extension_command_service.h b/chrome/browser/extensions/api/commands/extension_command_service.h
index 51ec0a1..1bb908b 100644
--- a/chrome/browser/extensions/api/commands/extension_command_service.h
+++ b/chrome/browser/extensions/api/commands/extension_command_service.h
@@ -88,7 +88,7 @@ class ExtensionCommandService : public ProfileKeyedService,
   // free, it will be taken by this extension. If not, that keybinding request
   // is ignored. |user_pref| is the PrefService used to record the new
   // keybinding assignment.
-  void AssignInitialKeybindings(const Extension* extension);
+  void AssignInitialKeybindings(const extensions::Extension* extension);
 
   // Removes all keybindings for a given extension by its |extension_id|.
   void RemoveKeybindingPrefs(std::string extension_id);
diff --git a/chrome/browser/extensions/api/context_menu/context_menu_apitest.cc b/chrome/browser/extensions/api/context_menu/context_menu_apitest.cc
index 094df01..0b8d2a1 100644
--- a/chrome/browser/extensions/api/context_menu/context_menu_apitest.cc
+++ b/chrome/browser/extensions/api/context_menu/context_menu_apitest.cc
@@ -24,7 +24,7 @@ IN_PROC_BROWSER_TEST_F(ExtensionApiTest, ContextMenusFromMultipleContexts) {
   ASSERT_TRUE(test_server()->Start());
   ASSERT_TRUE(RunExtensionTest("context_menus/add_from_multiple_contexts"))
       << message_;
-  const Extension* extension = GetSingleLoadedExtension();
+  const extensions::Extension* extension = GetSingleLoadedExtension();
   ASSERT_TRUE(extension) << message_;
 
   {
diff --git a/chrome/browser/extensions/api/cookies/cookies_api.cc b/chrome/browser/extensions/api/cookies/cookies_api.cc
index f36ea1a..e2cb2b0 100644
--- a/chrome/browser/extensions/api/cookies/cookies_api.cc
+++ b/chrome/browser/extensions/api/cookies/cookies_api.cc
@@ -290,7 +290,7 @@ void GetAllCookiesFunction::GetAllCookiesOnIOThread() {
 
 void GetAllCookiesFunction::GetAllCookiesCallback(
     const net::CookieList& cookie_list) {
-  const Extension* extension = GetExtension();
+  const extensions::Extension* extension = GetExtension();
   if (extension) {
     ListValue* matching_list = new ListValue();
     cookies_helpers::AppendMatchingCookiesToList(
diff --git a/chrome/browser/extensions/api/cookies/cookies_helpers.cc b/chrome/browser/extensions/api/cookies/cookies_helpers.cc
index 8322d2d..2a1c281 100644
--- a/chrome/browser/extensions/api/cookies/cookies_helpers.cc
+++ b/chrome/browser/extensions/api/cookies/cookies_helpers.cc
@@ -202,4 +202,4 @@ bool MatchFilter::MatchesDomain(const std::string& domain) {
 }
 
 }  // namespace cookies_helpers
-}  // namespace extensions
+}  // namespace extension
diff --git a/chrome/browser/extensions/api/cookies/cookies_helpers.h b/chrome/browser/extensions/api/cookies/cookies_helpers.h
index 464cfad..3ece5ba 100644
--- a/chrome/browser/extensions/api/cookies/cookies_helpers.h
+++ b/chrome/browser/extensions/api/cookies/cookies_helpers.h
@@ -16,7 +16,6 @@
 #include "net/cookies/cookie_monster.h"
 
 class Browser;
-class Extension;
 class Profile;
 
 namespace base {
@@ -25,6 +24,9 @@ class ListValue;
 }
 
 namespace extensions {
+
+class Extension;
+
 namespace cookies_helpers {
 
 // Returns either the original profile or the incognito profile, based on the
diff --git a/chrome/browser/extensions/api/dns/dns_apitest.cc b/chrome/browser/extensions/api/dns/dns_apitest.cc
index 6824507..b3746dc 100644
--- a/chrome/browser/extensions/api/dns/dns_apitest.cc
+++ b/chrome/browser/extensions/api/dns/dns_apitest.cc
@@ -100,7 +100,7 @@ const std::string DnsApiTest::kAddress = "9.8.7.6";
 IN_PROC_BROWSER_TEST_F(DnsApiTest, DnsResolveIPLiteral) {
   scoped_refptr<extensions::DnsResolveFunction> resolve_function(
       new extensions::DnsResolveFunction());
-  scoped_refptr<Extension> empty_extension(CreateEmptyExtension());
+  scoped_refptr<extensions::Extension> empty_extension(CreateEmptyExtension());
 
   resolve_function->set_extension(empty_extension.get());
   resolve_function->set_has_callback(true);
@@ -122,7 +122,7 @@ IN_PROC_BROWSER_TEST_F(DnsApiTest, DnsResolveIPLiteral) {
 IN_PROC_BROWSER_TEST_F(DnsApiTest, DnsResolveHostname) {
   scoped_refptr<extensions::DnsResolveFunction> resolve_function(
       new extensions::DnsResolveFunction());
-  scoped_refptr<Extension> empty_extension(CreateEmptyExtension());
+  scoped_refptr<extensions::Extension> empty_extension(CreateEmptyExtension());
 
   resolve_function->set_extension(empty_extension.get());
   resolve_function->set_has_callback(true);
diff --git a/chrome/browser/extensions/api/extension_action/browser_action_apitest.cc b/chrome/browser/extensions/api/extension_action/browser_action_apitest.cc
index 0043c26..5f7070c 100644
--- a/chrome/browser/extensions/api/extension_action/browser_action_apitest.cc
+++ b/chrome/browser/extensions/api/extension_action/browser_action_apitest.cc
@@ -26,6 +26,7 @@
 #include "ui/gfx/size.h"
 
 using content::WebContents;
+using extensions::Extension;
 
 class BrowserActionApiTest : public ExtensionApiTest {
  public:
diff --git a/chrome/browser/extensions/api/extension_action/page_action_apitest.cc b/chrome/browser/extensions/api/extension_action/page_action_apitest.cc
index 7591077..a221047 100644
--- a/chrome/browser/extensions/api/extension_action/page_action_apitest.cc
+++ b/chrome/browser/extensions/api/extension_action/page_action_apitest.cc
@@ -17,6 +17,8 @@
 #include "chrome/test/base/ui_test_utils.h"
 #include "content/public/browser/web_contents.h"
 
+using extensions::Extension;
+
 IN_PROC_BROWSER_TEST_F(ExtensionApiTest, PageAction) {
   ASSERT_TRUE(test_server()->Start());
   ASSERT_TRUE(RunExtensionTest("page_action/basics")) << message_;
diff --git a/chrome/browser/extensions/api/extension_action/page_as_browser_action_apitest.cc b/chrome/browser/extensions/api/extension_action/page_as_browser_action_apitest.cc
index 9d810e9..6beb603 100644
--- a/chrome/browser/extensions/api/extension_action/page_as_browser_action_apitest.cc
+++ b/chrome/browser/extensions/api/extension_action/page_as_browser_action_apitest.cc
@@ -24,6 +24,8 @@
 // These are a mash-up of the tests from from page_actions_apitest.cc and
 // browser_actions_apitest.cc.
 
+using extensions::Extension;
+
 namespace {
 
 class PageAsBrowserActionApiTest : public ExtensionApiTest {
diff --git a/chrome/browser/extensions/api/permissions/permissions_api.cc b/chrome/browser/extensions/api/permissions/permissions_api.cc
index e481c27..2c2f391 100644
--- a/chrome/browser/extensions/api/permissions/permissions_api.cc
+++ b/chrome/browser/extensions/api/permissions/permissions_api.cc
@@ -75,7 +75,7 @@ bool RemovePermissionsFunction::RunImpl() {
   if (!permissions.get())
     return false;
 
-  const Extension* extension = GetExtension();
+  const extensions::Extension* extension = GetExtension();
   ExtensionPermissionsInfo* info = ExtensionPermissionsInfo::GetInstance();
 
   // Make sure they're only trying to remove permissions supported by this API.
diff --git a/chrome/browser/extensions/api/permissions/permissions_api.h b/chrome/browser/extensions/api/permissions/permissions_api.h
index 97bf0ac..c954cc7 100644
--- a/chrome/browser/extensions/api/permissions/permissions_api.h
+++ b/chrome/browser/extensions/api/permissions/permissions_api.h
@@ -13,7 +13,6 @@
 #include "chrome/browser/extensions/extension_install_ui.h"
 #include "chrome/common/extensions/extension_permission_set.h"
 
-class Extension;
 class ExtensionPermissionSet;
 class ExtensionService;
 
diff --git a/chrome/browser/extensions/api/runtime/runtime_api.h b/chrome/browser/extensions/api/runtime/runtime_api.h
index b9e868b..1ff000d 100644
--- a/chrome/browser/extensions/api/runtime/runtime_api.h
+++ b/chrome/browser/extensions/api/runtime/runtime_api.h
@@ -8,12 +8,13 @@
 
 #include "chrome/browser/extensions/extension_function.h"
 
-class Extension;
 class ExtensionHost;
 class Profile;
 
 namespace extensions {
 
+class Extension;
+
 class RuntimeEventRouter {
  public:
   // Dispatches the onInstalled event to the given extension.
diff --git a/chrome/browser/extensions/api/socket/socket_apitest.cc b/chrome/browser/extensions/api/socket/socket_apitest.cc
index 8cdaef41..4143b3a 100644
--- a/chrome/browser/extensions/api/socket/socket_apitest.cc
+++ b/chrome/browser/extensions/api/socket/socket_apitest.cc
@@ -14,6 +14,8 @@
 #include "chrome/test/base/ui_test_utils.h"
 #include "net/test/test_server.h"
 
+using extensions::Extension;
+
 namespace utils = extension_function_test_utils;
 
 namespace {
diff --git a/chrome/browser/extensions/api/terminal/terminal_extension_helper.cc b/chrome/browser/extensions/api/terminal/terminal_extension_helper.cc
index cdbaea7..8cfe0154 100644
--- a/chrome/browser/extensions/api/terminal/terminal_extension_helper.cc
+++ b/chrome/browser/extensions/api/terminal/terminal_extension_helper.cc
@@ -12,7 +12,7 @@ namespace {
 
 const char kCroshExtensionEntryPoint[] = "/html/crosh.html";
 
-const Extension* GetTerminalExtension(Profile* profile) {
+const extensions::Extension* GetTerminalExtension(Profile* profile) {
   // Search order for terminal extensions.
   // We prefer hterm-dev, then hterm, then the builtin crosh extension.
   static const char* kPossibleAppIds[] = {
@@ -26,7 +26,7 @@ const Extension* GetTerminalExtension(Profile* profile) {
 
   ExtensionService* service = profile->GetExtensionService();
   for (size_t x = 0; x < arraysize(kPossibleAppIds); ++x) {
-    const Extension* extension = service->GetExtensionById(
+    const extensions::Extension* extension = service->GetExtensionById(
         kPossibleAppIds[x], false);
     if (extension)
       return extension;
@@ -38,7 +38,7 @@ const Extension* GetTerminalExtension(Profile* profile) {
 }  // namespace
 
 GURL TerminalExtensionHelper::GetCroshExtensionURL(Profile* profile) {
-  const Extension* extension = GetTerminalExtension(profile);
+  const extensions::Extension* extension = GetTerminalExtension(profile);
   if (!extension)
     return GURL();
 
diff --git a/chrome/browser/extensions/api/terminal/terminal_extension_helper.h b/chrome/browser/extensions/api/terminal/terminal_extension_helper.h
index ff82306..481f5a8 100644
--- a/chrome/browser/extensions/api/terminal/terminal_extension_helper.h
+++ b/chrome/browser/extensions/api/terminal/terminal_extension_helper.h
@@ -10,7 +10,6 @@
 
 #include "googleurl/src/gurl.h"
 
-class Extension;
 class Profile;
 
 class TerminalExtensionHelper {
diff --git a/chrome/browser/extensions/api/web_navigation/web_navigation_apitest.cc b/chrome/browser/extensions/api/web_navigation/web_navigation_apitest.cc
index 1152fcf..fef3a5b 100644
--- a/chrome/browser/extensions/api/web_navigation/web_navigation_apitest.cc
+++ b/chrome/browser/extensions/api/web_navigation/web_navigation_apitest.cc
@@ -189,7 +189,7 @@ IN_PROC_BROWSER_TEST_F(ExtensionApiTest, WebNavigationUserAction) {
   ResultCatcher catcher;
 
   ExtensionService* service = browser()->profile()->GetExtensionService();
-  const Extension* extension =
+  const extensions::Extension* extension =
       service->GetExtensionById(last_loaded_extension_id_, false);
   GURL url = extension->GetResourceURL("userAction/a.html");
 
@@ -227,7 +227,7 @@ IN_PROC_BROWSER_TEST_F(ExtensionApiTest, WebNavigationRequestOpenTab) {
   ResultCatcher catcher;
 
   ExtensionService* service = browser()->profile()->GetExtensionService();
-  const Extension* extension =
+  const extensions::Extension* extension =
       service->GetExtensionById(last_loaded_extension_id_, false);
   GURL url = extension->GetResourceURL("requestOpenTab/a.html");
 
diff --git a/chrome/browser/extensions/api/web_request/web_request_api.cc b/chrome/browser/extensions/api/web_request/web_request_api.cc
index 20616a8..0dbe7e4 100644
--- a/chrome/browser/extensions/api/web_request/web_request_api.cc
+++ b/chrome/browser/extensions/api/web_request/web_request_api.cc
@@ -51,6 +51,7 @@
 using content::BrowserMessageFilter;
 using content::BrowserThread;
 using content::ResourceRequestInfo;
+using extensions::Extension;
 
 namespace helpers = extension_web_request_api_helpers;
 namespace keys = extension_web_request_api_constants;
diff --git a/chrome/browser/extensions/api/web_request/web_request_apitest.cc b/chrome/browser/extensions/api/web_request/web_request_apitest.cc
index 63de52c..45a4ca9 100644
--- a/chrome/browser/extensions/api/web_request/web_request_apitest.cc
+++ b/chrome/browser/extensions/api/web_request/web_request_apitest.cc
@@ -105,7 +105,7 @@ IN_PROC_BROWSER_TEST_F(ExtensionWebRequestApiTest, WebRequestNewTab) {
   ResultCatcher catcher;
 
   ExtensionService* service = browser()->profile()->GetExtensionService();
-  const Extension* extension =
+  const extensions::Extension* extension =
       service->GetExtensionById(last_loaded_extension_id_, false);
   GURL url = extension->GetResourceURL("newTab/a.html");
 
diff --git a/chrome/browser/extensions/app_background_page_apitest.cc b/chrome/browser/extensions/app_background_page_apitest.cc
index 69cbc95..9a9a58c 100644
--- a/chrome/browser/extensions/app_background_page_apitest.cc
+++ b/chrome/browser/extensions/app_background_page_apitest.cc
@@ -20,6 +20,8 @@
 #include "content/test/test_notification_tracker.h"
 #include "net/base/mock_host_resolver.h"
 
+using extensions::Extension;
+
 class AppBackgroundPageApiTest : public ExtensionApiTest {
  public:
   void SetUpCommandLine(CommandLine* command_line) OVERRIDE {
diff --git a/chrome/browser/extensions/app_notification_browsertest.cc b/chrome/browser/extensions/app_notification_browsertest.cc
index bb833ab..87d4fec 100644
--- a/chrome/browser/extensions/app_notification_browsertest.cc
+++ b/chrome/browser/extensions/app_notification_browsertest.cc
@@ -54,7 +54,7 @@ IN_PROC_BROWSER_TEST_F(AppNotificationTest, SaveClientId) {
   Interceptor interceptor;
   AppNotifyChannelSetup::SetInterceptorForTests(&interceptor);
 
-  const Extension* app =
+  const extensions::Extension* app =
       LoadExtension(test_data_dir_.AppendASCII("app_notifications"));
   ASSERT_TRUE(app != NULL);
 
diff --git a/chrome/browser/extensions/app_notification_storage.cc b/chrome/browser/extensions/app_notification_storage.cc
index 42f11b2..b279170 100644
--- a/chrome/browser/extensions/app_notification_storage.cc
+++ b/chrome/browser/extensions/app_notification_storage.cc
@@ -131,7 +131,7 @@ bool LevelDbAppNotificationStorage::GetExtensionIds(
   scoped_ptr<leveldb::Iterator> iter(db_->NewIterator(read_options_));
   for (iter->SeekToFirst(); iter->Valid(); iter->Next()) {
     std::string key = iter->key().ToString();
-    if (Extension::IdIsValid(key))
+    if (extensions::Extension::IdIsValid(key))
       result->insert(key);
   }
 
diff --git a/chrome/browser/extensions/app_process_apitest.cc b/chrome/browser/extensions/app_process_apitest.cc
index a769286..c8d2774 100644
--- a/chrome/browser/extensions/app_process_apitest.cc
+++ b/chrome/browser/extensions/app_process_apitest.cc
@@ -30,6 +30,7 @@
 using content::NavigationController;
 using content::RenderViewHost;
 using content::WebContents;
+using extensions::Extension;
 
 // Simulates a page calling window.open on an URL, and waits for the navigation.
 static void WindowOpenHelper(Browser* browser,
diff --git a/chrome/browser/extensions/app_shortcut_manager.cc b/chrome/browser/extensions/app_shortcut_manager.cc
index bec3e3d..4d8fb70 100644
--- a/chrome/browser/extensions/app_shortcut_manager.cc
+++ b/chrome/browser/extensions/app_shortcut_manager.cc
@@ -17,6 +17,8 @@
 #include "skia/ext/image_operations.h"
 #include "ui/base/resource/resource_bundle.h"
 
+using extensions::Extension;
+
 namespace {
 // Allow tests to disable shortcut creation, to prevent developers' desktops
 // becoming overrun with shortcuts.
diff --git a/chrome/browser/extensions/app_shortcut_manager.h b/chrome/browser/extensions/app_shortcut_manager.h
index d97bbcc2..8868591 100644
--- a/chrome/browser/extensions/app_shortcut_manager.h
+++ b/chrome/browser/extensions/app_shortcut_manager.h
@@ -36,7 +36,7 @@ class AppShortcutManager : public ImageLoadingTracker::Observer,
   static void SetShortcutCreationDisabledForTesting(bool disabled);
  private:
   // Install the shortcuts for an application.
-  void InstallApplicationShortcuts(const Extension* extension);
+  void InstallApplicationShortcuts(const extensions::Extension* extension);
 
   content::NotificationRegistrar registrar_;
   Profile* profile_;
diff --git a/chrome/browser/extensions/app_sync_bundle.h b/chrome/browser/extensions/app_sync_bundle.h
index fd84b57..d3d444d 100644
--- a/chrome/browser/extensions/app_sync_bundle.h
+++ b/chrome/browser/extensions/app_sync_bundle.h
@@ -17,13 +17,14 @@
 #include "sync/api/syncable_service.h"
 
 class SyncChangeProcessor;
-class Extension;
 class ExtensionService;
 class ExtensionSet;
 class SyncErrorFactory;
 
 namespace extensions {
 
+class Extension;
+
 // Bundle of app specific sync stuff.
 class AppSyncBundle {
  public:
diff --git a/chrome/browser/extensions/app_sync_data.h b/chrome/browser/extensions/app_sync_data.h
index 3bdd335..d6c390f 100644
--- a/chrome/browser/extensions/app_sync_data.h
+++ b/chrome/browser/extensions/app_sync_data.h
@@ -10,7 +10,6 @@
 #include "chrome/common/string_ordinal.h"
 #include "sync/api/sync_change.h"
 
-class Extension;
 class SyncData;
 namespace sync_pb {
 class AppSpecifics;
@@ -18,6 +17,7 @@ class AppSpecifics;
 
 namespace extensions {
 
+class Extension;
 class ExtensionSyncData;
 
 // A class that encapsulates the synced properties of an Application.
diff --git a/chrome/browser/extensions/apps_promo.cc b/chrome/browser/extensions/apps_promo.cc
index b9d4365..70f0f64 100644
--- a/chrome/browser/extensions/apps_promo.cc
+++ b/chrome/browser/extensions/apps_promo.cc
@@ -202,7 +202,7 @@ AppsPromo::AppsPromo(PrefService* prefs)
 
 AppsPromo::~AppsPromo() {}
 
-bool AppsPromo::ShouldShowPromo(const ExtensionIdSet& installed_ids,
+bool AppsPromo::ShouldShowPromo(const extensions::ExtensionIdSet& installed_ids,
                                 bool* just_expired) {
   *just_expired = false;
 
@@ -253,7 +253,8 @@ bool AppsPromo::ShouldShowPromo(const ExtensionIdSet& installed_ids,
   return false;
 }
 
-bool AppsPromo::ShouldShowAppLauncher(const ExtensionIdSet& installed_ids) {
+bool AppsPromo::ShouldShowAppLauncher(
+    const extensions::ExtensionIdSet& installed_ids) {
   // On Chrome OS the default apps are installed via a separate mechanism that
   // is always enabled. Therefore we always show the launcher.
 #if defined(OS_CHROMEOS)
diff --git a/chrome/browser/extensions/apps_promo.h b/chrome/browser/extensions/apps_promo.h
index b132a39..3b25f5f 100644
--- a/chrome/browser/extensions/apps_promo.h
+++ b/chrome/browser/extensions/apps_promo.h
@@ -88,7 +88,7 @@ class AppsPromo {
 
   // Gets the set of old default apps that may have been installed by previous
   // versions of Chrome.
-  const ExtensionIdSet& old_default_apps() const {
+  const extensions::ExtensionIdSet& old_default_apps() const {
     return old_default_app_ids_;
   }
 
@@ -101,10 +101,10 @@ class AppsPromo {
   void HidePromo();
 
   // Returns true if the app launcher should be displayed on the NTP.
-  bool ShouldShowAppLauncher(const ExtensionIdSet& installed_ids);
+  bool ShouldShowAppLauncher(const extensions::ExtensionIdSet& installed_ids);
 
   // Returns true if the apps promo should be displayed in the launcher.
-  bool ShouldShowPromo(const ExtensionIdSet& installed_ids,
+  bool ShouldShowPromo(const extensions::ExtensionIdSet& installed_ids,
                        bool* just_expired);
 
  private:
@@ -136,7 +136,7 @@ class AppsPromo {
 
   // The set of default extensions. Initialized to a static list in the
   // constructor.
-  ExtensionIdSet old_default_app_ids_;
+  extensions::ExtensionIdSet old_default_app_ids_;
 
   DISALLOW_COPY_AND_ASSIGN(AppsPromo);
 };
diff --git a/chrome/browser/extensions/apps_promo_unittest.cc b/chrome/browser/extensions/apps_promo_unittest.cc
index e4e470c..b9e2e5e 100644
--- a/chrome/browser/extensions/apps_promo_unittest.cc
+++ b/chrome/browser/extensions/apps_promo_unittest.cc
@@ -57,7 +57,8 @@ void ExtensionAppsPromo::SetUp() {
 #if !defined(OS_CHROMEOS)
 
 TEST_F(ExtensionAppsPromo, HappyPath) {
-  const ExtensionIdSet& default_app_ids = apps_promo()->old_default_apps();
+  const extensions::ExtensionIdSet& default_app_ids =
+      apps_promo()->old_default_apps();
 
   EXPECT_GT(default_app_ids.size(), 0u);
 
@@ -68,7 +69,7 @@ TEST_F(ExtensionAppsPromo, HappyPath) {
 
   // The app launcher and promo should not be shown if there are no extensions
   // installed and no promo is set.
-  ExtensionIdSet installed_ids;
+  extensions::ExtensionIdSet installed_ids;
   bool promo_just_expired = false;
   EXPECT_FALSE(AppsPromo::IsPromoSupportedForLocale());
   EXPECT_FALSE(apps_promo()->ShouldShowAppLauncher(installed_ids));
diff --git a/chrome/browser/extensions/chrome_app_api_browsertest.cc b/chrome/browser/extensions/chrome_app_api_browsertest.cc
index 865c44e..c0b3eae 100644
--- a/chrome/browser/extensions/chrome_app_api_browsertest.cc
+++ b/chrome/browser/extensions/chrome_app_api_browsertest.cc
@@ -21,6 +21,8 @@
 #include "googleurl/src/gurl.h"
 #include "net/base/mock_host_resolver.h"
 
+using extensions::Extension;
+
 class ChromeAppAPITest : public ExtensionBrowserTest {
  protected:
   bool IsAppInstalled() { return IsAppInstalled(L""); }
diff --git a/chrome/browser/extensions/component_loader.h b/chrome/browser/extensions/component_loader.h
index e6b24b9..f0be4c2 100644
--- a/chrome/browser/extensions/component_loader.h
+++ b/chrome/browser/extensions/component_loader.h
@@ -15,12 +15,13 @@
 #include "chrome/browser/prefs/pref_change_registrar.h"
 #include "content/public/browser/notification_observer.h"
 
-class Extension;
 class ExtensionServiceInterface;
 class PrefService;
 
 namespace extensions {
 
+class Extension;
+
 // For registering, loading, and unloading component extensions.
 class ComponentLoader : public content::NotificationObserver {
  public:
diff --git a/chrome/browser/extensions/component_loader_unittest.cc b/chrome/browser/extensions/component_loader_unittest.cc
index 2830c8b..e076ba1 100644
--- a/chrome/browser/extensions/component_loader_unittest.cc
+++ b/chrome/browser/extensions/component_loader_unittest.cc
@@ -16,6 +16,8 @@
 #include "chrome/test/base/testing_pref_service.h"
 #include "testing/gtest/include/gtest/gtest.h"
 
+using extensions::Extension;
+
 namespace {
 
 class MockExtensionService : public TestExtensionService {
diff --git a/chrome/browser/extensions/content_script_apitest.cc b/chrome/browser/extensions/content_script_apitest.cc
index 0e75dc7..0d1c901 100644
--- a/chrome/browser/extensions/content_script_apitest.cc
+++ b/chrome/browser/extensions/content_script_apitest.cc
@@ -125,7 +125,7 @@ IN_PROC_BROWSER_TEST_F(ExtensionApiTest, ContentScriptExtensionAPIs) {
 
   CommandLine::ForCurrentProcess()->AppendSwitch(
       switches::kEnableExperimentalExtensionApis);
-  const Extension* extension = LoadExtension(
+  const extensions::Extension* extension = LoadExtension(
       test_data_dir_.AppendASCII("content_scripts/extension_api"));
 
   ResultCatcher catcher;
diff --git a/chrome/browser/extensions/convert_user_script.cc b/chrome/browser/extensions/convert_user_script.cc
index f73dc3b..92fadbd 100644
--- a/chrome/browser/extensions/convert_user_script.cc
+++ b/chrome/browser/extensions/convert_user_script.cc
@@ -24,6 +24,8 @@
 #include "crypto/sha2.h"
 #include "googleurl/src/gurl.h"
 
+using extensions::Extension;
+
 namespace keys = extension_manifest_keys;
 namespace values = extension_manifest_values;
 
diff --git a/chrome/browser/extensions/convert_user_script.h b/chrome/browser/extensions/convert_user_script.h
index 8a8933a..109a4ce 100644
--- a/chrome/browser/extensions/convert_user_script.h
+++ b/chrome/browser/extensions/convert_user_script.h
@@ -11,10 +11,13 @@
 #include "base/memory/ref_counted.h"
 #include "base/string16.h"
 
-class Extension;
 class FilePath;
 class GURL;
 
+namespace extensions {
+class Extension;
+}
+
 // Wraps the specified user script in an extension. The extension is created
 // unpacked in the system temp dir. Returns a valid extension that the caller
 // should take ownership on success, or NULL and |error| on failure.
@@ -22,7 +25,7 @@ class GURL;
 // NOTE: This function does file IO and should not be called on the UI thread.
 // NOTE: The caller takes ownership of the directory at extension->path() on the
 // returned object.
-scoped_refptr<Extension> ConvertUserScriptToExtension(
+scoped_refptr<extensions::Extension> ConvertUserScriptToExtension(
     const FilePath& user_script, const GURL& original_url, string16* error);
 
 #endif  // CHROME_BROWSER_EXTENSIONS_CONVERT_USER_SCRIPT_H_
diff --git a/chrome/browser/extensions/convert_user_script_unittest.cc b/chrome/browser/extensions/convert_user_script_unittest.cc
index 1ab3a9b..cafdbe8 100644
--- a/chrome/browser/extensions/convert_user_script_unittest.cc
+++ b/chrome/browser/extensions/convert_user_script_unittest.cc
@@ -16,6 +16,8 @@
 #include "chrome/common/extensions/extension.h"
 #include "testing/gtest/include/gtest/gtest.h"
 
+using extensions::Extension;
+
 namespace {
 
 static void AddPattern(URLPatternSet* extent, const std::string& pattern) {
diff --git a/chrome/browser/extensions/convert_web_app.cc b/chrome/browser/extensions/convert_web_app.cc
index bafb5d9..bd36cb5 100644
--- a/chrome/browser/extensions/convert_web_app.cc
+++ b/chrome/browser/extensions/convert_web_app.cc
@@ -32,6 +32,7 @@
 namespace keys = extension_manifest_keys;
 
 using base::Time;
+using extensions::Extension;
 
 namespace {
 
diff --git a/chrome/browser/extensions/convert_web_app.h b/chrome/browser/extensions/convert_web_app.h
index 0ce2814..4aecb5d 100644
--- a/chrome/browser/extensions/convert_web_app.h
+++ b/chrome/browser/extensions/convert_web_app.h
@@ -10,12 +10,15 @@
 
 #include "base/memory/ref_counted.h"
 
-class Extension;
 
 namespace base {
 class Time;
 }
 
+namespace extensions {
+class Extension;
+}
+
 struct WebApplicationInfo;
 
 // Generates a version number for an extension from a time. The goal is to make
@@ -36,7 +39,7 @@ std::string ConvertTimeToExtensionVersion(const base::Time& time);
 // NOTE: This function does file IO and should not be called on the UI thread.
 // NOTE: The caller takes ownership of the directory at extension->path() on the
 // returned object.
-scoped_refptr<Extension> ConvertWebAppToExtension(
+scoped_refptr<extensions::Extension> ConvertWebAppToExtension(
     const WebApplicationInfo& web_app_info,
     const base::Time& create_time);
 
diff --git a/chrome/browser/extensions/convert_web_app_browsertest.cc b/chrome/browser/extensions/convert_web_app_browsertest.cc
index 3210d58..7ec70b9 100644
--- a/chrome/browser/extensions/convert_web_app_browsertest.cc
+++ b/chrome/browser/extensions/convert_web_app_browsertest.cc
@@ -24,7 +24,7 @@ class ExtensionFromWebAppTest
   }
 
   std::string expected_extension_id_;
-  const Extension* installed_extension_;
+  const extensions::Extension* installed_extension_;
 
  private:
   // InProcessBrowserTest
@@ -37,8 +37,8 @@ class ExtensionFromWebAppTest
                        const content::NotificationSource& source,
                        const content::NotificationDetails& details) {
     if (type == chrome::NOTIFICATION_EXTENSION_INSTALLED) {
-      const Extension* extension =
-          content::Details<const Extension>(details).ptr();
+      const extensions::Extension* extension =
+          content::Details<const extensions::Extension>(details).ptr();
       if (extension->id() == expected_extension_id_) {
         installed_extension_ = extension;
         MessageLoopForUI::current()->Quit();
diff --git a/chrome/browser/extensions/convert_web_app_unittest.cc b/chrome/browser/extensions/convert_web_app_unittest.cc
index 640b31b..4a8b257 100644
--- a/chrome/browser/extensions/convert_web_app_unittest.cc
+++ b/chrome/browser/extensions/convert_web_app_unittest.cc
@@ -105,7 +105,7 @@ TEST(ExtensionFromWebApp, Basic) {
     web_app.icons.push_back(GetIconInfo(icon_url, sizes[i]));
   }
 
-  scoped_refptr<Extension> extension = ConvertWebAppToExtension(
+  scoped_refptr<extensions::Extension> extension = ConvertWebAppToExtension(
       web_app, GetTestTime(1978, 12, 11, 0, 0, 0, 0));
   ASSERT_TRUE(extension.get());
 
@@ -148,7 +148,7 @@ TEST(ExtensionFromWebApp, Minimal) {
   web_app.title = ASCIIToUTF16("Gearpad");
   web_app.app_url = GURL("http://aaronboodman.com/gearpad/");
 
-  scoped_refptr<Extension> extension = ConvertWebAppToExtension(
+  scoped_refptr<extensions::Extension> extension = ConvertWebAppToExtension(
       web_app, GetTestTime(1978, 12, 11, 0, 0, 0, 0));
   ASSERT_TRUE(extension.get());
 
diff --git a/chrome/browser/extensions/crx_installer.cc b/chrome/browser/extensions/crx_installer.cc
index 687a777..4a26f21 100644
--- a/chrome/browser/extensions/crx_installer.cc
+++ b/chrome/browser/extensions/crx_installer.cc
@@ -49,6 +49,7 @@
 
 using content::BrowserThread;
 using content::UserMetricsAction;
+using extensions::Extension;
 using extensions::PermissionsUpdater;
 
 // static
diff --git a/chrome/browser/extensions/crx_installer.h b/chrome/browser/extensions/crx_installer.h
index c5acf80..e8d9114 100644
--- a/chrome/browser/extensions/crx_installer.h
+++ b/chrome/browser/extensions/crx_installer.h
@@ -90,8 +90,10 @@ class CrxInstaller
 
   const FilePath& source_file() const { return source_file_; }
 
-  Extension::Location install_source() const { return install_source_; }
-  void set_install_source(Extension::Location source) {
+  extensions::Extension::Location install_source() const {
+    return install_source_;
+  }
+  void set_install_source(extensions::Extension::Location source) {
     install_source_ = source;
   }
 
@@ -109,13 +111,13 @@ class CrxInstaller
   void set_allow_silent_install(bool val) { allow_silent_install_ = val; }
 
   bool is_gallery_install() const {
-    return (creation_flags_ & Extension::FROM_WEBSTORE) > 0;
+    return (creation_flags_ & extensions::Extension::FROM_WEBSTORE) > 0;
   }
   void set_is_gallery_install(bool val) {
     if (val)
-      creation_flags_ |= Extension::FROM_WEBSTORE;
+      creation_flags_ |= extensions::Extension::FROM_WEBSTORE;
     else
-      creation_flags_ &= ~Extension::FROM_WEBSTORE;
+      creation_flags_ &= ~extensions::Extension::FROM_WEBSTORE;
   }
 
   // The original download URL should be set when the WebstoreInstaller is
@@ -167,14 +169,14 @@ class CrxInstaller
 
   // Called after OnUnpackSuccess as a last check to see whether the install
   // should complete.
-  bool AllowInstall(const Extension* extension, string16* error);
+  bool AllowInstall(const extensions::Extension* extension, string16* error);
 
   // SandboxedExtensionUnpackerClient
   virtual void OnUnpackFailure(const string16& error_message) OVERRIDE;
   virtual void OnUnpackSuccess(const FilePath& temp_dir,
                                const FilePath& extension_dir,
                                const base::DictionaryValue* original_manifest,
-                               const Extension* extension) OVERRIDE;
+                               const extensions::Extension* extension) OVERRIDE;
 
   // Returns true if we can skip confirmation because the install was
   // whitelisted.
@@ -193,7 +195,7 @@ class CrxInstaller
   void ReportFailureFromUIThread(const string16& error);
   void ReportSuccessFromFileThread();
   void ReportSuccessFromUIThread();
-  void NotifyCrxInstallComplete(const Extension* extension);
+  void NotifyCrxInstallComplete(const extensions::Extension* extension);
 
   // The file we're installing.
   FilePath source_file_;
@@ -207,7 +209,7 @@ class CrxInstaller
   // The location the installation came from (bundled with Chromium, registry,
   // manual install, etc). This metadata is saved with the installation if
   // successful. Defaults to INTERNAL.
-  Extension::Location install_source_;
+  extensions::Extension::Location install_source_;
 
   // Indicates whether the user has already approved the extension to be
   // installed. If true, |expected_manifest_| and |expected_id_| must match
@@ -248,7 +250,7 @@ class CrxInstaller
 
   // The extension we're installing. We own this and either pass it off to
   // ExtensionService on success, or delete it on failure.
-  scoped_refptr<const Extension> extension_;
+  scoped_refptr<const extensions::Extension> extension_;
 
   // The ordinal of the NTP apps page |extension_| will be shown on.
   StringOrdinal page_ordinal_;
diff --git a/chrome/browser/extensions/crx_installer_browsertest.cc b/chrome/browser/extensions/crx_installer_browsertest.cc
index efaaf0a..8a0c4bd 100644
--- a/chrome/browser/extensions/crx_installer_browsertest.cc
+++ b/chrome/browser/extensions/crx_installer_browsertest.cc
@@ -32,11 +32,13 @@ class MockInstallUI : public ExtensionInstallUI {
   bool confirmation_requested() { return confirmation_requested_; }
 
   // Overriding some of the ExtensionInstallUI API.
-  void ConfirmInstall(Delegate* delegate, const Extension* extension) {
+  void ConfirmInstall(Delegate* delegate,
+                      const extensions::Extension* extension) {
     confirmation_requested_ = true;
     delegate->InstallUIProceed();
   }
-  void OnInstallSuccess(const Extension* extension, SkBitmap* icon) {
+  void OnInstallSuccess(const extensions::Extension* extension,
+                        SkBitmap* icon) {
     MessageLoopForUI::current()->Quit();
   }
   void OnInstallFailure(const string16& error) {
diff --git a/chrome/browser/extensions/default_apps.cc b/chrome/browser/extensions/default_apps.cc
index 71d0c2d..0d7821c 100644
--- a/chrome/browser/extensions/default_apps.cc
+++ b/chrome/browser/extensions/default_apps.cc
@@ -12,6 +12,7 @@
 #include "chrome/browser/prefs/pref_service.h"
 #include "chrome/browser/profiles/profile.h"
 #include "chrome/common/chrome_switches.h"
+#include "chrome/common/extensions/extension.h"
 #include "chrome/common/pref_names.h"
 #include "ui/base/l10n/l10n_util.h"
 
@@ -117,8 +118,8 @@ void RegisterUserPrefs(PrefService* prefs) {
 Provider::Provider(Profile* profile,
                    VisitorInterface* service,
                    ExternalExtensionLoader* loader,
-                   Extension::Location crx_location,
-                   Extension::Location download_location,
+                   extensions::Extension::Location crx_location,
+                   extensions::Extension::Location download_location,
                    int creation_flags)
     : ExternalExtensionProviderImpl(service, loader, crx_location,
                                     download_location, creation_flags),
diff --git a/chrome/browser/extensions/default_apps.h b/chrome/browser/extensions/default_apps.h
index 2904114..254fa86 100644
--- a/chrome/browser/extensions/default_apps.h
+++ b/chrome/browser/extensions/default_apps.h
@@ -12,6 +12,10 @@
 class PrefService;
 class Profile;
 
+namespace extensions {
+class Extension;
+}
+
 // Functions and types related to installing default apps.
 namespace default_apps {
 
@@ -36,8 +40,8 @@ class Provider : public ExternalExtensionProviderImpl {
   Provider(Profile* profile,
            VisitorInterface* service,
            ExternalExtensionLoader* loader,
-           Extension::Location crx_location,
-           Extension::Location download_location,
+           extensions::Extension::Location crx_location,
+           extensions::Extension::Location download_location,
            int creation_flags);
 
   // ExternalExtensionProviderImpl overrides:
diff --git a/chrome/browser/extensions/execute_code_in_tab_function.cc b/chrome/browser/extensions/execute_code_in_tab_function.cc
index d50afc6..9786b9c 100644
--- a/chrome/browser/extensions/execute_code_in_tab_function.cc
+++ b/chrome/browser/extensions/execute_code_in_tab_function.cc
@@ -157,7 +157,7 @@ void ExecuteCodeInTabFunction::OnExecuteCodeFinished(bool success,
 void ExecuteCodeInTabFunction::DidLoadFile(bool success,
                                            const std::string& data) {
   std::string function_name = name();
-  const Extension* extension = GetExtension();
+  const extensions::Extension* extension = GetExtension();
 
   // Check if the file is CSS and needs localization.
   if (success &&
@@ -231,7 +231,7 @@ bool ExecuteCodeInTabFunction::Execute(const std::string& code_string) {
     return false;
   }
 
-  const Extension* extension = GetExtension();
+  const extensions::Extension* extension = GetExtension();
   if (!extension) {
     SendResponse(false);
     return false;
diff --git a/chrome/browser/extensions/extension_activity_log.cc b/chrome/browser/extensions/extension_activity_log.cc
index 85ad4d2..ea9a048 100644
--- a/chrome/browser/extensions/extension_activity_log.cc
+++ b/chrome/browser/extensions/extension_activity_log.cc
@@ -23,7 +23,7 @@ ExtensionActivityLog* ExtensionActivityLog::GetInstance() {
 }
 
 void ExtensionActivityLog::AddObserver(
-    const Extension* extension,
+    const extensions::Extension* extension,
     ExtensionActivityLog::Observer* observer) {
   base::AutoLock scoped_lock(lock_);
 
@@ -35,7 +35,7 @@ void ExtensionActivityLog::AddObserver(
 }
 
 void ExtensionActivityLog::RemoveObserver(
-    const Extension* extension,
+    const extensions::Extension* extension,
     ExtensionActivityLog::Observer* observer) {
   base::AutoLock scoped_lock(lock_);
 
@@ -43,8 +43,9 @@ void ExtensionActivityLog::RemoveObserver(
     observers_[extension]->RemoveObserver(observer);
   }
 }
-
-bool ExtensionActivityLog::HasObservers(const Extension* extension) const {
+// Extension*
+bool ExtensionActivityLog::HasObservers(
+    const extensions::Extension* extension) const {
   base::AutoLock scoped_lock(lock_);
 
   // We also return true if extension activity logging is enabled since in that
@@ -52,7 +53,7 @@ bool ExtensionActivityLog::HasObservers(const Extension* extension) const {
   return observers_.count(extension) > 0 || log_activity_to_stdout_;
 }
 
-void ExtensionActivityLog::Log(const Extension* extension,
+void ExtensionActivityLog::Log(const extensions::Extension* extension,
                                Activity activity,
                                const std::string& msg) const {
   base::AutoLock scoped_lock(lock_);
diff --git a/chrome/browser/extensions/extension_activity_log.h b/chrome/browser/extensions/extension_activity_log.h
index 1c18077..ffef1d6 100644
--- a/chrome/browser/extensions/extension_activity_log.h
+++ b/chrome/browser/extensions/extension_activity_log.h
@@ -12,7 +12,9 @@
 #include "base/observer_list_threadsafe.h"
 #include "base/synchronization/lock.h"
 
+namespace extensions {
 class Extension;
+}
 
 // A utility for tracing interesting activity for each extension.
 class ExtensionActivityLog {
@@ -25,7 +27,7 @@ class ExtensionActivityLog {
   // Observers can listen for activity events.
   class Observer {
    public:
-    virtual void OnExtensionActivity(const Extension* extension,
+    virtual void OnExtensionActivity(const extensions::Extension* extension,
                                      Activity activity,
                                      const std::string& msg) = 0;
   };
@@ -34,14 +36,15 @@ class ExtensionActivityLog {
   static ExtensionActivityLog* GetInstance();
 
   // Add/remove observer.
-  void AddObserver(const Extension* extension, Observer* observer);
-  void RemoveObserver(const Extension* extension, Observer* observer);
+  void AddObserver(const extensions::Extension* extension, Observer* observer);
+  void RemoveObserver(const extensions::Extension* extension,
+                      Observer* observer);
 
   // Check for the existence observer list by extension_id.
-  bool HasObservers(const Extension* extension) const;
+  bool HasObservers(const extensions::Extension* extension) const;
 
   // Log |activity| for |extension|.
-  void Log(const Extension* extension,
+  void Log(const extensions::Extension* extension,
            Activity activity,
            const std::string& msg) const;
 
@@ -59,7 +62,8 @@ class ExtensionActivityLog {
   bool log_activity_to_stdout_;
 
   typedef ObserverListThreadSafe<Observer> ObserverList;
-  typedef std::map<const Extension*, scoped_refptr<ObserverList> > ObserverMap;
+  typedef std::map<const extensions::Extension*, scoped_refptr<ObserverList> >
+      ObserverMap;
   // A map of extensions to activity observers for that extension.
   ObserverMap observers_;
 
diff --git a/chrome/browser/extensions/extension_apitest.cc b/chrome/browser/extensions/extension_apitest.cc
index cce2618..6678901 100644
--- a/chrome/browser/extensions/extension_apitest.cc
+++ b/chrome/browser/extensions/extension_apitest.cc
@@ -174,7 +174,7 @@ bool ExtensionApiTest::RunExtensionTestImpl(const char* extension_name,
   DCHECK(!std::string(extension_name).empty() || !page_url.empty()) <<
       "extension_name and page_url cannot both be empty";
 
-  const Extension* extension = NULL;
+  const extensions::Extension* extension = NULL;
   if (!std::string(extension_name).empty()) {
     FilePath extension_path = test_data_dir_.AppendASCII(extension_name);
     if (load_as_component) {
@@ -226,15 +226,15 @@ bool ExtensionApiTest::RunExtensionTestImpl(const char* extension_name,
 }
 
 // Test that exactly one extension is loaded, and return it.
-const Extension* ExtensionApiTest::GetSingleLoadedExtension() {
+const extensions::Extension* ExtensionApiTest::GetSingleLoadedExtension() {
   ExtensionService* service = browser()->profile()->GetExtensionService();
 
-  const Extension* extension = NULL;
+  const extensions::Extension* extension = NULL;
   for (ExtensionSet::const_iterator it = service->extensions()->begin();
        it != service->extensions()->end(); ++it) {
     // Ignore any component extensions. They are automatically loaded into all
     // profiles and aren't the extension we're looking for here.
-    if ((*it)->location() == Extension::COMPONENT)
+    if ((*it)->location() == extensions::Extension::COMPONENT)
       continue;
 
     if (extension != NULL) {
diff --git a/chrome/browser/extensions/extension_apitest.h b/chrome/browser/extensions/extension_apitest.h
index 28ec8b4..9e34373 100644
--- a/chrome/browser/extensions/extension_apitest.h
+++ b/chrome/browser/extensions/extension_apitest.h
@@ -14,13 +14,16 @@
 #include "chrome/browser/extensions/extension_browsertest.h"
 #include "content/public/browser/notification_registrar.h"
 
+class FilePath;
+
+namespace extensions {
+class Extension;
+}
+
 namespace ui_test_utils {
 class TestWebSocketServer;
 }
 
-class Extension;
-class FilePath;
-
 // The general flow of these API tests should work like this:
 // (1) Setup initial browser state (e.g. create some bookmarks for the
 //     bookmark test)
@@ -148,7 +151,7 @@ class ExtensionApiTest : public ExtensionBrowserTest {
 
   // Test that exactly one extension loaded.  If so, return a pointer to
   // the extension.  If not, return NULL and set message_.
-  const Extension* GetSingleLoadedExtension();
+  const extensions::Extension* GetSingleLoadedExtension();
 
   // All extensions tested by ExtensionApiTest are in the "api_test" dir.
   virtual void SetUpCommandLine(CommandLine* command_line) OVERRIDE;
diff --git a/chrome/browser/extensions/extension_browser_event_router.cc b/chrome/browser/extensions/extension_browser_event_router.cc
index d39810e..8be4717 100644
--- a/chrome/browser/extensions/extension_browser_event_router.cc
+++ b/chrome/browser/extensions/extension_browser_event_router.cc
@@ -676,7 +676,7 @@ void ExtensionBrowserEventRouter::ExtensionActionExecuted(
     Profile* profile,
     const std::string& extension_id,
     TabContentsWrapper* tab_contents) {
-  const Extension* extension =
+  const extensions::Extension* extension =
       profile->GetExtensionService()->GetExtensionById(extension_id, false);
   if (!extension)
     return;
diff --git a/chrome/browser/extensions/extension_browsertest.cc b/chrome/browser/extensions/extension_browsertest.cc
index a75649e..5297e1d 100644
--- a/chrome/browser/extensions/extension_browsertest.cc
+++ b/chrome/browser/extensions/extension_browsertest.cc
@@ -32,6 +32,8 @@
 #include "content/public/browser/notification_service.h"
 #include "content/public/browser/render_view_host.h"
 
+using extensions::Extension;
+
 ExtensionBrowserTest::ExtensionBrowserTest()
     : loaded_(false),
       installed_(false),
diff --git a/chrome/browser/extensions/extension_browsertest.h b/chrome/browser/extensions/extension_browsertest.h
index 2489445..19141d5 100644
--- a/chrome/browser/extensions/extension_browsertest.h
+++ b/chrome/browser/extensions/extension_browsertest.h
@@ -17,7 +17,9 @@
 #include "content/public/browser/notification_observer.h"
 #include "content/public/browser/notification_types.h"
 
+namespace extensions {
 class Extension;
+}
 
 // Base class for extension browser tests. Provides utilities for loading,
 // unloading, and installing extensions.
@@ -30,17 +32,17 @@ class ExtensionBrowserTest
   // InProcessBrowserTest
   virtual void SetUpCommandLine(CommandLine* command_line) OVERRIDE;
 
-  const Extension* LoadExtension(const FilePath& path);
+  const extensions::Extension* LoadExtension(const FilePath& path);
 
   // Same as above, but enables the extension in incognito mode first.
-  const Extension* LoadExtensionIncognito(const FilePath& path);
+  const extensions::Extension* LoadExtensionIncognito(const FilePath& path);
 
-  const Extension* LoadExtensionWithOptions(const FilePath& path,
+  const extensions::Extension* LoadExtensionWithOptions(const FilePath& path,
                                             bool incognito_enabled,
                                             bool fileaccess_enabled);
 
   // Loads extension and imitates that it is a component extension.
-  const Extension* LoadExtensionAsComponent(const FilePath& path);
+  const extensions::Extension* LoadExtensionAsComponent(const FilePath& path);
 
   // Pack the extension in |dir_path| into a crx file and return its path.
   // Return an empty FilePath if there were errors.
@@ -59,18 +61,20 @@ class ExtensionBrowserTest
   // disabled, if negative).
   // 1 means you expect a new install, 0 means you expect an upgrade, -1 means
   // you expect a failed upgrade.
-  const Extension* InstallExtension(const FilePath& path, int expected_change) {
+  const extensions::Extension* InstallExtension(const FilePath& path,
+                                                int expected_change) {
     return InstallOrUpdateExtension("", path, INSTALL_UI_TYPE_NONE,
                                     expected_change);
   }
 
   // Installs extension as if it came from the Chrome Webstore.
-  const Extension* InstallExtensionFromWebstore(
+  const extensions::Extension* InstallExtensionFromWebstore(
       const FilePath& path, int expected_change);
 
   // Same as above but passes an id to CrxInstaller and does not allow a
   // privilege increase.
-  const Extension* UpdateExtension(const std::string& id, const FilePath& path,
+  const extensions::Extension* UpdateExtension(const std::string& id,
+                                               const FilePath& path,
                                    int expected_change) {
     return InstallOrUpdateExtension(id, path, INSTALL_UI_TYPE_NONE,
                                     expected_change);
@@ -78,20 +82,22 @@ class ExtensionBrowserTest
 
   // Same as |InstallExtension| but with the normal extension UI showing up
   // (for e.g. info bar on success).
-  const Extension* InstallExtensionWithUI(const FilePath& path,
-                                          int expected_change) {
+  const extensions::Extension* InstallExtensionWithUI(const FilePath& path,
+                                                      int expected_change) {
     return InstallOrUpdateExtension("", path, INSTALL_UI_TYPE_NORMAL,
                                     expected_change);
   }
-  const Extension* InstallExtensionWithUIAutoConfirm(const FilePath& path,
-                                                     int expected_change,
-                                                     Profile* profile) {
+
+  const extensions::Extension* InstallExtensionWithUIAutoConfirm(
+      const FilePath& path,
+      int expected_change,
+      Profile* profile) {
     return InstallOrUpdateExtension("", path, INSTALL_UI_TYPE_AUTO_CONFIRM,
                                     expected_change, profile, false);
   }
 
   // Begins install process but simulates a user cancel.
-  const Extension* StartInstallButCancel(const FilePath& path) {
+  const extensions::Extension* StartInstallButCancel(const FilePath& path) {
     return InstallOrUpdateExtension("", path, INSTALL_UI_TYPE_CANCEL, 0);
   }
 
@@ -157,16 +163,16 @@ class ExtensionBrowserTest
     INSTALL_UI_TYPE_AUTO_CONFIRM,
   };
 
-  const Extension* InstallOrUpdateExtension(const std::string& id,
-                                            const FilePath& path,
-                                            InstallUIType ui_type,
-                                            int expected_change);
-  const Extension* InstallOrUpdateExtension(const std::string& id,
-                                            const FilePath& path,
-                                            InstallUIType ui_type,
-                                            int expected_change,
-                                            Profile* profile,
-                                            bool from_webstore);
+  const extensions::Extension* InstallOrUpdateExtension(const std::string& id,
+                                                        const FilePath& path,
+                                                        InstallUIType ui_type,
+                                                        int expected_change);
+  const extensions::Extension* InstallOrUpdateExtension(const std::string& id,
+                                                        const FilePath& path,
+                                                        InstallUIType ui_type,
+                                                        int expected_change,
+                                                        Profile* profile,
+                                                        bool from_webstore);
 
   bool WaitForExtensionViewsToLoad();
 
diff --git a/chrome/browser/extensions/extension_browsertests_misc.cc b/chrome/browser/extensions/extension_browsertests_misc.cc
index 78481b0..0e27f41 100644
--- a/chrome/browser/extensions/extension_browsertests_misc.cc
+++ b/chrome/browser/extensions/extension_browsertests_misc.cc
@@ -34,6 +34,7 @@
 
 using content::NavigationController;
 using content::WebContents;
+using extensions::Extension;
 
 const std::string kSubscribePage = "/subscribe.html";
 const std::string kFeedPage = "files/feeds/feed.html";
diff --git a/chrome/browser/extensions/extension_context_menu_browsertest.cc b/chrome/browser/extensions/extension_context_menu_browsertest.cc
index 83bb8bb..c4e06d4 100644
--- a/chrome/browser/extensions/extension_context_menu_browsertest.cc
+++ b/chrome/browser/extensions/extension_context_menu_browsertest.cc
@@ -156,7 +156,7 @@ class ExtensionContextMenuBrowserTest : public ExtensionBrowserTest {
 
   // Returns a pointer to the currently loaded extension with |name|, or null
   // if not found.
-  const Extension* GetExtensionNamed(std::string name) {
+  const extensions::Extension* GetExtensionNamed(std::string name) {
     const ExtensionSet* extensions =
         browser()->profile()->GetExtensionService()->extensions();
     ExtensionSet::const_iterator i;
@@ -357,7 +357,7 @@ static void VerifyMenuForSeparatorsTest(const MenuModel& menu) {
 IN_PROC_BROWSER_TEST_F(ExtensionContextMenuBrowserTest, Separators) {
   // Load the extension.
   ASSERT_TRUE(LoadContextMenuExtension("separators"));
-  const Extension* extension = GetExtensionNamed("Separators Test");
+  const extensions::Extension* extension = GetExtensionNamed("Separators Test");
   ASSERT_TRUE(extension != NULL);
 
   // Navigate to test1.html inside the extension, which should create a bunch
diff --git a/chrome/browser/extensions/extension_context_menu_model.cc b/chrome/browser/extensions/extension_context_menu_model.cc
index f336b7c..92eceed 100644
--- a/chrome/browser/extensions/extension_context_menu_model.cc
+++ b/chrome/browser/extensions/extension_context_menu_model.cc
@@ -23,6 +23,7 @@
 using content::OpenURLParams;
 using content::Referrer;
 using content::WebContents;
+using extensions::Extension;
 
 enum MenuEntries {
   NAME = 0,
diff --git a/chrome/browser/extensions/extension_context_menu_model.h b/chrome/browser/extensions/extension_context_menu_model.h
index 059907fe..1f0134c 100644
--- a/chrome/browser/extensions/extension_context_menu_model.h
+++ b/chrome/browser/extensions/extension_context_menu_model.h
@@ -13,10 +13,13 @@
 #include "ui/base/models/simple_menu_model.h"
 
 class Browser;
-class Extension;
 class ExtensionAction;
 class Profile;
 
+namespace extensions {
+class Extension;
+}
+
 // The menu model for the context menu for extension action icons (browser and
 // page actions).
 class ExtensionContextMenuModel
@@ -26,7 +29,8 @@ class ExtensionContextMenuModel
       public ExtensionUninstallDialog::Delegate {
  public:
   // Creates a menu model for the given extension action.
-  ExtensionContextMenuModel(const Extension* extension, Browser* browser);
+  ExtensionContextMenuModel(const extensions::Extension* extension,
+                            Browser* browser);
 
   // SimpleMenuModel::Delegate overrides.
   virtual bool IsCommandIdChecked(int command_id) const OVERRIDE;
@@ -48,7 +52,7 @@ class ExtensionContextMenuModel
 
   // Gets the extension we are displaying the menu for. Returns NULL if the
   // extension has been uninstalled and no longer exists.
-  const Extension* GetExtension() const;
+  const extensions::Extension* GetExtension() const;
 
   // A copy of the extension's id.
   std::string extension_id_;
diff --git a/chrome/browser/extensions/extension_crash_recovery_browsertest.cc b/chrome/browser/extensions/extension_crash_recovery_browsertest.cc
index 3e69eb0..2341cf2 100644
--- a/chrome/browser/extensions/extension_crash_recovery_browsertest.cc
+++ b/chrome/browser/extensions/extension_crash_recovery_browsertest.cc
@@ -27,6 +27,7 @@
 
 using content::NavigationController;
 using content::WebContents;
+using extensions::Extension;
 
 class ExtensionCrashRecoveryTest : public ExtensionBrowserTest {
  protected:
diff --git a/chrome/browser/extensions/extension_creator.cc b/chrome/browser/extensions/extension_creator.cc
index 5550c2f..0aaa77f 100644
--- a/chrome/browser/extensions/extension_creator.cc
+++ b/chrome/browser/extensions/extension_creator.cc
@@ -23,6 +23,8 @@
 #include "grit/generated_resources.h"
 #include "ui/base/l10n/l10n_util.h"
 
+using extensions::Extension;
+
 namespace {
   const int kRSAKeySize = 1024;
 };
diff --git a/chrome/browser/extensions/extension_debugger_api.cc b/chrome/browser/extensions/extension_debugger_api.cc
index 1330c3d..da4a530 100644
--- a/chrome/browser/extensions/extension_debugger_api.cc
+++ b/chrome/browser/extensions/extension_debugger_api.cc
@@ -269,7 +269,8 @@ void ExtensionDevToolsClientHost::Observe(
     const content::NotificationDetails& details) {
   if (type == chrome::NOTIFICATION_EXTENSION_UNLOADED) {
     std::string id =
-        content::Details<UnloadedExtensionInfo>(details)->extension->id();
+        content::Details<extensions::UnloadedExtensionInfo>(details)->
+            extension->id();
     if (id == extension_id_)
         Close();
   } else {
diff --git a/chrome/browser/extensions/extension_disabled_ui.cc b/chrome/browser/extensions/extension_disabled_ui.cc
index 3f37118..e1af856 100644
--- a/chrome/browser/extensions/extension_disabled_ui.cc
+++ b/chrome/browser/extensions/extension_disabled_ui.cc
@@ -33,6 +33,8 @@
 #include "grit/theme_resources.h"
 #include "ui/base/l10n/l10n_util.h"
 
+using extensions::Extension;
+
 namespace {
 
 static base::LazyInstance<
@@ -290,8 +292,8 @@ void ExtensionDisabledGlobalError::Observe(
     extension = content::Details<const Extension>(details).ptr();
   } else {
     DCHECK_EQ(chrome::NOTIFICATION_EXTENSION_UNLOADED, type);
-    UnloadedExtensionInfo* info =
-        content::Details<UnloadedExtensionInfo>(details).ptr();
+    extensions::UnloadedExtensionInfo* info =
+        content::Details<extensions::UnloadedExtensionInfo>(details).ptr();
     extension = info->extension;
   }
   if (extension == extension_) {
diff --git a/chrome/browser/extensions/extension_disabled_ui.h b/chrome/browser/extensions/extension_disabled_ui.h
index f033b8e..1899cf3 100644
--- a/chrome/browser/extensions/extension_disabled_ui.h
+++ b/chrome/browser/extensions/extension_disabled_ui.h
@@ -6,12 +6,13 @@
 #define CHROME_BROWSER_EXTENSIONS_EXTENSION_DISABLED_UI_H_
 #pragma once
 
-class Extension;
 class ExtensionService;
 class Profile;
 
 namespace extensions {
 
+class Extension;
+
 // Adds a global error to inform the user that an extension was
 // disabled after upgrading to higher permissions.
 void AddExtensionDisabledError(ExtensionService* service,
diff --git a/chrome/browser/extensions/extension_disabled_ui_browsertest.cc b/chrome/browser/extensions/extension_disabled_ui_browsertest.cc
index 8d30040..9a2889b1c 100644
--- a/chrome/browser/extensions/extension_disabled_ui_browsertest.cc
+++ b/chrome/browser/extensions/extension_disabled_ui_browsertest.cc
@@ -15,6 +15,8 @@
 #include "chrome/browser/ui/global_error_service_factory.h"
 #include "chrome/common/extensions/extension.h"
 
+using extensions::Extension;
+
 class ExtensionDisabledGlobalErrorTest : public ExtensionBrowserTest {
  protected:
   void SetUpOnMainThread() {
diff --git a/chrome/browser/extensions/extension_event_router.cc b/chrome/browser/extensions/extension_event_router.cc
index 8b27f22..041d566 100644
--- a/chrome/browser/extensions/extension_event_router.cc
+++ b/chrome/browser/extensions/extension_event_router.cc
@@ -31,6 +31,7 @@
 #include "content/public/browser/render_process_host.h"
 
 using content::BrowserThread;
+using extensions::Extension;
 using extensions::ExtensionAPI;
 
 namespace {
@@ -487,8 +488,8 @@ void ExtensionEventRouter::Observe(
     }
     case chrome::NOTIFICATION_EXTENSION_UNLOADED: {
       // Remove all registered lazy listeners from our cache.
-      UnloadedExtensionInfo* unloaded =
-          content::Details<UnloadedExtensionInfo>(details).ptr();
+      extensions::UnloadedExtensionInfo* unloaded =
+          content::Details<extensions::UnloadedExtensionInfo>(details).ptr();
       ListenerProcess lazy_listener(NULL, unloaded->extension->id());
       for (ListenerMap::iterator it = lazy_listeners_.begin();
            it != lazy_listeners_.end(); ++it) {
diff --git a/chrome/browser/extensions/extension_event_router.h b/chrome/browser/extensions/extension_event_router.h
index faf80e9..42a649c 100644
--- a/chrome/browser/extensions/extension_event_router.h
+++ b/chrome/browser/extensions/extension_event_router.h
@@ -18,7 +18,6 @@
 #include "ipc/ipc_message.h"
 
 class GURL;
-class Extension;
 class ExtensionHost;
 class ExtensionDevToolsManager;
 class Profile;
@@ -27,6 +26,10 @@ namespace content {
 class RenderProcessHost;
 }
 
+namespace extensions {
+class Extension;
+}
+
 class ExtensionEventRouter : public content::NotificationObserver {
  public:
   // These constants convey the state of our knowledge of whether we're in
@@ -163,7 +166,7 @@ class ExtensionEventRouter : public content::NotificationObserver {
   // the event crosses the incognito boundary.
   bool CanDispatchEventToProfile(
       Profile* profile,
-      const Extension* extension,
+      const extensions::Extension* extension,
       const linked_ptr<ExtensionEvent>& event,
       const std::string** event_args);
 
@@ -179,12 +182,13 @@ class ExtensionEventRouter : public content::NotificationObserver {
   // dispatch an event.
   void MaybeLoadLazyBackgroundPage(
       Profile* profile,
-      const Extension* extension,
+      const extensions::Extension* extension,
       const linked_ptr<ExtensionEvent>& event);
 
   // Track of the number of dispatched events that have not yet sent an
   // ACK from the renderer.
-  void IncrementInFlightEvents(Profile* profile, const Extension* extension);
+  void IncrementInFlightEvents(Profile* profile,
+                               const extensions::Extension* extension);
 
   void DispatchPendingEvent(const linked_ptr<ExtensionEvent>& event,
                             ExtensionHost* host);
diff --git a/chrome/browser/extensions/extension_function.h b/chrome/browser/extensions/extension_function.h
index d943a31b..caef240 100644
--- a/chrome/browser/extensions/extension_function.h
+++ b/chrome/browser/extensions/extension_function.h
@@ -124,8 +124,10 @@ class ExtensionFunction
   void set_profile_id(void* profile_id) { profile_id_ = profile_id; }
   void* profile_id() const { return profile_id_; }
 
-  void set_extension(const Extension* extension) { extension_ = extension; }
-  const Extension* GetExtension() const { return extension_.get(); }
+  void set_extension(const extensions::Extension* extension) {
+    extension_ = extension;
+  }
+  const extensions::Extension* GetExtension() const { return extension_.get(); }
   const std::string& extension_id() const { return extension_->id(); }
 
   void set_request_id(int request_id) { request_id_ = request_id; }
@@ -181,7 +183,7 @@ class ExtensionFunction
   void* profile_id_;
 
   // The extension that called this function.
-  scoped_refptr<const Extension> extension_;
+  scoped_refptr<const extensions::Extension> extension_;
 
   // The name of this function.
   std::string name_;
diff --git a/chrome/browser/extensions/extension_function_dispatcher.cc b/chrome/browser/extensions/extension_function_dispatcher.cc
index 113fcbf..3bde203 100644
--- a/chrome/browser/extensions/extension_function_dispatcher.cc
+++ b/chrome/browser/extensions/extension_function_dispatcher.cc
@@ -34,6 +34,7 @@
 #include "third_party/skia/include/core/SkBitmap.h"
 #include "webkit/glue/resource_type.h"
 
+using extensions::Extension;
 using extensions::ExtensionAPI;
 using content::RenderViewHost;
 using WebKit::WebSecurityOrigin;
diff --git a/chrome/browser/extensions/extension_function_dispatcher.h b/chrome/browser/extensions/extension_function_dispatcher.h
index 5278171..ed6548a 100644
--- a/chrome/browser/extensions/extension_function_dispatcher.h
+++ b/chrome/browser/extensions/extension_function_dispatcher.h
@@ -15,7 +15,6 @@
 #include "googleurl/src/gurl.h"
 
 class ChromeRenderMessageFilter;
-class Extension;
 class ExtensionFunction;
 class ExtensionWindowController;
 class ExtensionInfoMap;
@@ -28,6 +27,7 @@ class WebContents;
 }
 
 namespace extensions {
+class Extension;
 class ExtensionAPI;
 class ProcessMap;
 }
@@ -104,7 +104,7 @@ class ExtensionFunctionDispatcher
 
   // Called when an ExtensionFunction is done executing, after it has sent
   // a response (if any) to the extension.
-  void OnExtensionFunctionCompleted(const Extension* extension);
+  void OnExtensionFunctionCompleted(const extensions::Extension* extension);
 
   // The profile that this dispatcher is associated with.
   Profile* profile() { return profile_; }
@@ -115,7 +115,7 @@ class ExtensionFunctionDispatcher
   // Does not set subclass properties, or include_incognito.
   static ExtensionFunction* CreateExtensionFunction(
       const ExtensionHostMsg_Request_Params& params,
-      const Extension* extension,
+      const extensions::Extension* extension,
       int requesting_process_id,
       const extensions::ProcessMap& process_map,
       extensions::ExtensionAPI* api,
diff --git a/chrome/browser/extensions/extension_function_test_utils.cc b/chrome/browser/extensions/extension_function_test_utils.cc
index 8b33ed1..2f0fc46 100644
--- a/chrome/browser/extensions/extension_function_test_utils.cc
+++ b/chrome/browser/extensions/extension_function_test_utils.cc
@@ -17,6 +17,7 @@
 #include "testing/gtest/include/gtest/gtest.h"
 
 using content::WebContents;
+using extensions::Extension;
 
 namespace {
 
diff --git a/chrome/browser/extensions/extension_function_test_utils.h b/chrome/browser/extensions/extension_function_test_utils.h
index 27336a5..3ae6db8 100644
--- a/chrome/browser/extensions/extension_function_test_utils.h
+++ b/chrome/browser/extensions/extension_function_test_utils.h
@@ -13,7 +13,6 @@
 
 class AsyncExtensionFunction;
 class Browser;
-class Extension;
 class UIThreadExtensionFunction;
 
 namespace base {
@@ -22,6 +21,10 @@ class DictionaryValue;
 class ListValue;
 }
 
+namespace extensions {
+class Extension;
+}
+
 namespace extension_function_test_utils {
 
 // Parse JSON and return as the specified type, or NULL if the JSON is invalid
@@ -45,12 +48,12 @@ base::ListValue* ToList(base::Value* val);
 
 // Creates an extension instance that can be attached to an ExtensionFunction
 // before running it.
-scoped_refptr<Extension> CreateEmptyExtension();
+scoped_refptr<extensions::Extension> CreateEmptyExtension();
 
 // Creates an extension instance with a specified location that can be attached
 // to an ExtensionFunction before running.
-scoped_refptr<Extension> CreateEmptyExtensionWithLocation(
-    Extension::Location location);
+scoped_refptr<extensions::Extension> CreateEmptyExtensionWithLocation(
+    extensions::Extension::Location location);
 
 enum RunFunctionFlags {
   NONE = 0,
diff --git a/chrome/browser/extensions/extension_global_error.cc b/chrome/browser/extensions/extension_global_error.cc
index 3a69833..9217de4 100644
--- a/chrome/browser/extensions/extension_global_error.cc
+++ b/chrome/browser/extensions/extension_global_error.cc
@@ -13,6 +13,8 @@
 #include "grit/generated_resources.h"
 #include "ui/base/l10n/l10n_util.h"
 
+using extensions::ExtensionIdSet;
+
 ExtensionGlobalError::ExtensionGlobalError(ExtensionService* extension_service)
     : extension_service_(extension_service),
       external_extension_ids_(new ExtensionIdSet),
@@ -75,7 +77,8 @@ string16 ExtensionGlobalError::GenerateMessageSection(
 
   for (ExtensionIdSet::const_iterator iter = extensions->begin();
        iter != extensions->end(); ++iter) {
-    const Extension* e = extension_service_->GetExtensionById(*iter, true);
+    const extensions::Extension* e = extension_service_->GetExtensionById(*iter,
+        true);
     message += l10n_util::GetStringFUTF16(template_message_id,
                                           string16(ASCIIToUTF16(e->name())));
   }
diff --git a/chrome/browser/extensions/extension_global_error.h b/chrome/browser/extensions/extension_global_error.h
index 7a45468..1b02e88 100644
--- a/chrome/browser/extensions/extension_global_error.h
+++ b/chrome/browser/extensions/extension_global_error.h
@@ -29,15 +29,15 @@ class ExtensionGlobalError : public GlobalError {
 
   // Returns sets replaying the IDs that have been added with the
   // Add[...]Extension methods.
-  const ExtensionIdSet* get_external_extension_ids() const {
+  const extensions::ExtensionIdSet* get_external_extension_ids() const {
     return external_extension_ids_.get();
   }
 
-  const ExtensionIdSet* get_blacklisted_extension_ids() const {
+  const extensions::ExtensionIdSet* get_blacklisted_extension_ids() const {
     return blacklisted_extension_ids_.get();
   }
 
-  const ExtensionIdSet* get_orphaned_extension_ids() const {
+  const extensions::ExtensionIdSet* get_orphaned_extension_ids() const {
     return orphaned_extension_ids_.get();
   }
 
@@ -59,14 +59,14 @@ class ExtensionGlobalError : public GlobalError {
  private:
   bool should_delete_self_on_close_;
   ExtensionService* extension_service_;
-  scoped_ptr<ExtensionIdSet> external_extension_ids_;
-  scoped_ptr<ExtensionIdSet> blacklisted_extension_ids_;
-  scoped_ptr<ExtensionIdSet> orphaned_extension_ids_;
+  scoped_ptr<extensions::ExtensionIdSet> external_extension_ids_;
+  scoped_ptr<extensions::ExtensionIdSet> blacklisted_extension_ids_;
+  scoped_ptr<extensions::ExtensionIdSet> orphaned_extension_ids_;
   string16 message_;  // Displayed in the body of the alert.
 
   // For a given set of extension IDs, generates appropriate text
   // describing what the user needs to know about them.
-  string16 GenerateMessageSection(const ExtensionIdSet* extensions,
+  string16 GenerateMessageSection(const extensions::ExtensionIdSet* extensions,
                                   int template_message_id);
 
   // Generates the message displayed in the body of the alert.
diff --git a/chrome/browser/extensions/extension_host.cc b/chrome/browser/extensions/extension_host.cc
index e5088af..ea90c45 100644
--- a/chrome/browser/extensions/extension_host.cc
+++ b/chrome/browser/extensions/extension_host.cc
@@ -123,7 +123,7 @@ class ExtensionHost::ProcessCreationQueue {
 ////////////////
 // ExtensionHost
 
-ExtensionHost::ExtensionHost(const Extension* extension,
+ExtensionHost::ExtensionHost(const extensions::Extension* extension,
                              SiteInstance* site_instance,
                              const GURL& url,
                              content::ViewType host_type)
@@ -245,7 +245,7 @@ void ExtensionHost::LoadInitialURL() {
       !profile_->GetExtensionService()->IsBackgroundPageReady(extension_)) {
     // Make sure the background page loads before any others.
     registrar_.Add(this, chrome::NOTIFICATION_EXTENSION_BACKGROUND_PAGE_READY,
-                   content::Source<Extension>(extension_));
+                   content::Source<extensions::Extension>(extension_));
     return;
   }
 
@@ -276,7 +276,8 @@ void ExtensionHost::Observe(int type,
       // when multiple ExtensionHost objects pointing to the same Extension are
       // present.
       if (extension_ ==
-          content::Details<UnloadedExtensionInfo>(details)->extension) {
+          content::Details<extensions::UnloadedExtensionInfo>(
+              details)->extension) {
         extension_ = NULL;
       }
       break;
diff --git a/chrome/browser/extensions/extension_host.h b/chrome/browser/extensions/extension_host.h
index a9aa8e2..4350872 100644
--- a/chrome/browser/extensions/extension_host.h
+++ b/chrome/browser/extensions/extension_host.h
@@ -31,7 +31,6 @@
 #endif
 
 class Browser;
-class Extension;
 class ExtensionWindowController;
 class PrefsTabHelper;
 
@@ -41,6 +40,10 @@ class RenderWidgetHostView;
 class SiteInstance;
 }
 
+namespace extensions {
+class Extension;
+}
+
 // This class is the browser component of an extension component's RenderView.
 // It handles setting up the renderer process, if needed, with special
 // privileges available to extensions.  It may have a view to be shown in the
@@ -63,7 +66,7 @@ class ExtensionHost : public content::WebContentsDelegate,
   typedef ExtensionViewAndroid PlatformExtensionView;
 #endif
 
-  ExtensionHost(const Extension* extension,
+  ExtensionHost(const extensions::Extension* extension,
                 content::SiteInstance* site_instance,
                 const GURL& url, content::ViewType host_type);
   virtual ~ExtensionHost();
@@ -92,7 +95,7 @@ class ExtensionHost : public content::WebContentsDelegate,
   // instantiate Browser objects.
   void CreateView(Browser* browser);
 
-  const Extension* extension() const { return extension_; }
+  const extensions::Extension* extension() const { return extension_; }
   const std::string& extension_id() const { return extension_id_; }
   content::WebContents* host_contents() const { return host_contents_.get(); }
   content::RenderViewHost* render_view_host() const;
@@ -199,7 +202,7 @@ class ExtensionHost : public content::WebContentsDelegate,
   bool is_background_page() const { return !view(); }
 
   // The extension that we're hosting in this view.
-  const Extension* extension_;
+  const extensions::Extension* extension_;
 
   // Id of extension that we're hosting in this view.
   const std::string extension_id_;
diff --git a/chrome/browser/extensions/extension_host_mac.h b/chrome/browser/extensions/extension_host_mac.h
index 1ee25a6..4f655e4 100644
--- a/chrome/browser/extensions/extension_host_mac.h
+++ b/chrome/browser/extensions/extension_host_mac.h
@@ -8,11 +8,15 @@
 
 #include "chrome/browser/extensions/extension_host.h"
 
+namespace extensions {
+class Extension;
+}
+
 // TODO(mpcomplete): I don't know what this does or if it is needed anymore,
 // now that ExtensionHost is restructured to rely on WebContents.
 class ExtensionHostMac : public ExtensionHost {
  public:
-  ExtensionHostMac(const Extension* extension,
+  ExtensionHostMac(const extensions::Extension* extension,
                    content::SiteInstance* site_instance,
                    const GURL& url, content::ViewType host_type) :
       ExtensionHost(extension, site_instance, url, host_type) {}
diff --git a/chrome/browser/extensions/extension_icon_manager.cc b/chrome/browser/extensions/extension_icon_manager.cc
index 37d17fe..c81fee6 100644
--- a/chrome/browser/extensions/extension_icon_manager.cc
+++ b/chrome/browser/extensions/extension_icon_manager.cc
@@ -46,7 +46,7 @@ ExtensionIconManager::ExtensionIconManager()
 ExtensionIconManager::~ExtensionIconManager() {
 }
 
-void ExtensionIconManager::LoadIcon(const Extension* extension) {
+void ExtensionIconManager::LoadIcon(const extensions::Extension* extension) {
   ExtensionResource icon_resource = extension->GetIconResource(
       ExtensionIconSet::EXTENSION_ICON_BITTY, ExtensionIconSet::MATCH_BIGGER);
   if (!icon_resource.extension_root().empty()) {
diff --git a/chrome/browser/extensions/extension_icon_manager.h b/chrome/browser/extensions/extension_icon_manager.h
index 4596d12..d7863db 100644
--- a/chrome/browser/extensions/extension_icon_manager.h
+++ b/chrome/browser/extensions/extension_icon_manager.h
@@ -15,7 +15,9 @@
 #include "third_party/skia/include/core/SkBitmap.h"
 #include "ui/gfx/insets.h"
 
+namespace extensions {
 class Extension;
+}
 
 class ExtensionIconManager : public ImageLoadingTracker::Observer {
  public:
@@ -23,7 +25,7 @@ class ExtensionIconManager : public ImageLoadingTracker::Observer {
   virtual ~ExtensionIconManager();
 
   // Start loading the icon for the given extension.
-  void LoadIcon(const Extension* extension);
+  void LoadIcon(const extensions::Extension* extension);
 
   // This returns a bitmap of width/height kFaviconSize, loaded either from an
   // entry specified in the extension's 'icon' section of the manifest, or a
diff --git a/chrome/browser/extensions/extension_icon_manager_unittest.cc b/chrome/browser/extensions/extension_icon_manager_unittest.cc
index b058153..615ae8d 100644
--- a/chrome/browser/extensions/extension_icon_manager_unittest.cc
+++ b/chrome/browser/extensions/extension_icon_manager_unittest.cc
@@ -15,6 +15,7 @@
 #include "ui/gfx/skia_util.h"
 
 using content::BrowserThread;
+using extensions::Extension;
 
 // Our test class that takes care of managing the necessary threads for loading
 // extension icons, and waiting for those loads to happen.
diff --git a/chrome/browser/extensions/extension_info_map.cc b/chrome/browser/extensions/extension_info_map.cc
index 8db94d5..8401ceb 100644
--- a/chrome/browser/extensions/extension_info_map.cc
+++ b/chrome/browser/extensions/extension_info_map.cc
@@ -10,6 +10,7 @@
 #include "content/public/browser/browser_thread.h"
 
 using content::BrowserThread;
+using extensions::Extension;
 
 namespace {
 
diff --git a/chrome/browser/extensions/extension_info_map.h b/chrome/browser/extensions/extension_info_map.h
index df8a6c5..8a64d55 100644
--- a/chrome/browser/extensions/extension_info_map.h
+++ b/chrome/browser/extensions/extension_info_map.h
@@ -17,7 +17,9 @@
 #include "chrome/common/extensions/extension_constants.h"
 #include "chrome/common/extensions/extension_set.h"
 
+namespace extensions {
 class Extension;
+}
 
 // Contains extension data that needs to be accessed on the IO thread. It can
 // be created/destroyed on any thread, but all other methods must be called on
@@ -34,7 +36,7 @@ class ExtensionInfoMap : public base::RefCountedThreadSafe<ExtensionInfoMap> {
   const extensions::ProcessMap& process_map() const;
 
   // Callback for when new extensions are loaded.
-  void AddExtension(const Extension* extension,
+  void AddExtension(const extensions::Extension* extension,
                     base::Time install_time,
                     bool incognito_enabled);
 
@@ -51,7 +53,7 @@ class ExtensionInfoMap : public base::RefCountedThreadSafe<ExtensionInfoMap> {
 
   // Returns true if the given extension can see events and data from another
   // sub-profile (incognito to original profile, or vice versa).
-  bool CanCrossIncognito(const Extension* extension);
+  bool CanCrossIncognito(const extensions::Extension* extension);
 
   // Adds an entry to process_map_.
   void RegisterExtensionProcess(const std::string& extension_id,
diff --git a/chrome/browser/extensions/extension_info_map_unittest.cc b/chrome/browser/extensions/extension_info_map_unittest.cc
index 65d95a6..1317c9e 100644
--- a/chrome/browser/extensions/extension_info_map_unittest.cc
+++ b/chrome/browser/extensions/extension_info_map_unittest.cc
@@ -15,6 +15,7 @@
 #include "third_party/WebKit/Source/WebKit/chromium/public/platform/WebURL.h"
 
 using content::BrowserThread;
+using extensions::Extension;
 using WebKit::WebSecurityOrigin;
 using WebKit::WebString;
 
diff --git a/chrome/browser/extensions/extension_infobar_delegate.cc b/chrome/browser/extensions/extension_infobar_delegate.cc
index 0418d68..8f9d8c7 100644
--- a/chrome/browser/extensions/extension_infobar_delegate.cc
+++ b/chrome/browser/extensions/extension_infobar_delegate.cc
@@ -18,7 +18,7 @@
 ExtensionInfoBarDelegate::ExtensionInfoBarDelegate(
     Browser* browser,
     InfoBarTabHelper* infobar_helper,
-    const Extension* extension,
+    const extensions::Extension* extension,
     const GURL& url,
     int height)
         : InfoBarDelegate(infobar_helper),
@@ -97,7 +97,8 @@ void ExtensionInfoBarDelegate::Observe(
   } else {
     DCHECK(type == chrome::NOTIFICATION_EXTENSION_UNLOADED);
     if (extension_ ==
-        content::Details<UnloadedExtensionInfo>(details)->extension) {
+        content::Details<extensions::UnloadedExtensionInfo>(
+            details)->extension) {
       RemoveSelf();
     }
   }
diff --git a/chrome/browser/extensions/extension_infobar_delegate.h b/chrome/browser/extensions/extension_infobar_delegate.h
index 0e230e1..a8205bd 100644
--- a/chrome/browser/extensions/extension_infobar_delegate.h
+++ b/chrome/browser/extensions/extension_infobar_delegate.h
@@ -12,10 +12,13 @@
 #include "content/public/browser/notification_registrar.h"
 
 class Browser;
-class Extension;
 class ExtensionHost;
 class GURL;
 
+namespace extensions {
+class Extension;
+}
+
 // The InfobarDelegate for creating and managing state for the ExtensionInfobar
 // plus monitor when the extension goes away.
 class ExtensionInfoBarDelegate : public InfoBarDelegate,
@@ -32,11 +35,11 @@ class ExtensionInfoBarDelegate : public InfoBarDelegate,
 
   ExtensionInfoBarDelegate(Browser* browser,
                            InfoBarTabHelper* infobar_helper,
-                           const Extension* extension,
+                           const extensions::Extension* extension,
                            const GURL& url,
                            int height);
 
-  const Extension* extension() { return extension_; }
+  const extensions::Extension* extension() { return extension_; }
   ExtensionHost* extension_host() { return extension_host_.get(); }
   int height() { return height_; }
 
@@ -70,7 +73,7 @@ class ExtensionInfoBarDelegate : public InfoBarDelegate,
   // The observer monitoring when the delegate dies.
   DelegateObserver* observer_;
 
-  const Extension* extension_;
+  const extensions::Extension* extension_;
   content::NotificationRegistrar registrar_;
 
   // The requested height of the infobar (in pixels).
diff --git a/chrome/browser/extensions/extension_input_ime_api.cc b/chrome/browser/extensions/extension_input_ime_api.cc
index 181d147..0ef52e7 100644
--- a/chrome/browser/extensions/extension_input_ime_api.cc
+++ b/chrome/browser/extensions/extension_input_ime_api.cc
@@ -326,7 +326,7 @@ void ExtensionInputImeEventRouter::Init() {}
 bool ExtensionInputImeEventRouter::RegisterIme(
     Profile* profile,
     const std::string& extension_id,
-    const Extension::InputComponentInfo& component) {
+    const extensions::Extension::InputComponentInfo& component) {
   VLOG(1) << "RegisterIme: " << extension_id << " id: " << component.id;
 
   std::map<std::string, chromeos::InputMethodEngine*>& engine_map =
diff --git a/chrome/browser/extensions/extension_input_ime_api.h b/chrome/browser/extensions/extension_input_ime_api.h
index ddee364..1220871 100644
--- a/chrome/browser/extensions/extension_input_ime_api.h
+++ b/chrome/browser/extensions/extension_input_ime_api.h
@@ -31,7 +31,7 @@ class ExtensionInputImeEventRouter {
 
   bool RegisterIme(Profile* profile,
                    const std::string& extension_id,
-                   const Extension::InputComponentInfo& component);
+                   const extensions::Extension::InputComponentInfo& component);
   void UnregisterAllImes(Profile* profile, const std::string& extension_id);
   chromeos::InputMethodEngine* GetEngine(const std::string& extension_id,
                                          const std::string& engine_id);
diff --git a/chrome/browser/extensions/extension_install_dialog.h b/chrome/browser/extensions/extension_install_dialog.h
index 7ecdc27..9aabe0c 100644
--- a/chrome/browser/extensions/extension_install_dialog.h
+++ b/chrome/browser/extensions/extension_install_dialog.h
@@ -12,7 +12,6 @@
 #include "base/string16.h"
 #include "chrome/browser/extensions/extension_install_ui.h"
 
-class Extension;
 class Profile;
 class SkBitmap;
 
diff --git a/chrome/browser/extensions/extension_install_ui.cc b/chrome/browser/extensions/extension_install_ui.cc
index db904af..ad858d3 100644
--- a/chrome/browser/extensions/extension_install_ui.cc
+++ b/chrome/browser/extensions/extension_install_ui.cc
@@ -51,6 +51,7 @@
 
 using content::WebContents;
 using extensions::BundleInstaller;
+using extensions::Extension;
 
 static const int kTitleIds[ExtensionInstallUI::NUM_PROMPT_TYPES] = {
   0,  // The regular install prompt depends on what's being installed.
diff --git a/chrome/browser/extensions/extension_install_ui.h b/chrome/browser/extensions/extension_install_ui.h
index 372c627..4f6307d 100644
--- a/chrome/browser/extensions/extension_install_ui.h
+++ b/chrome/browser/extensions/extension_install_ui.h
@@ -18,7 +18,6 @@
 #include "ui/gfx/native_widget_types.h"
 
 class Browser;
-class Extension;
 class ExtensionPermissionSet;
 class MessageLoop;
 class Profile;
@@ -27,11 +26,12 @@ class TabContentsWrapper;
 
 namespace base {
 class DictionaryValue;
-}  // namespace base
+}
 
 namespace extensions {
 class BundleInstaller;
-}  // namespace extensions
+class Extension;
+}
 
 // Displays all the UI around extension installation.
 class ExtensionInstallUI : public ImageLoadingTracker::Observer {
@@ -92,8 +92,10 @@ class ExtensionInstallUI : public ImageLoadingTracker::Observer {
     }
 
     // Populated for all other types.
-    const Extension* extension() const { return extension_; }
-    void set_extension(const Extension* extension) { extension_ = extension; }
+    const extensions::Extension* extension() const { return extension_; }
+    void set_extension(const extensions::Extension* extension) {
+      extension_ = extension;
+    }
 
     const gfx::Image& icon() const { return icon_; }
     void set_icon(const gfx::Image& icon) { icon_ = icon; }
@@ -105,7 +107,7 @@ class ExtensionInstallUI : public ImageLoadingTracker::Observer {
     std::vector<string16> permissions_;
 
     // The extension or bundle being installed.
-    const Extension* extension_;
+    const extensions::Extension* extension_;
     const extensions::BundleInstaller* bundle_;
 
     // The icon to be displayed.
@@ -138,7 +140,7 @@ class ExtensionInstallUI : public ImageLoadingTracker::Observer {
 
   // Creates a dummy extension from the |manifest|, replacing the name and
   // description with the localizations if provided.
-  static scoped_refptr<Extension> GetLocalizedExtensionForDisplay(
+  static scoped_refptr<extensions::Extension> GetLocalizedExtensionForDisplay(
       const base::DictionaryValue* manifest,
       const std::string& id,
       const std::string& localized_name,
@@ -173,7 +175,7 @@ class ExtensionInstallUI : public ImageLoadingTracker::Observer {
   //
   // We *MUST* eventually call either Proceed() or Abort() on |delegate|.
   virtual void ConfirmInlineInstall(Delegate* delegate,
-                                    const Extension* extension,
+                                    const extensions::Extension* extension,
                                     SkBitmap* icon,
                                     const Prompt& prompt);
 
@@ -182,31 +184,34 @@ class ExtensionInstallUI : public ImageLoadingTracker::Observer {
   //
   // We *MUST* eventually call either Proceed() or Abort() on |delegate|.
   virtual void ConfirmWebstoreInstall(Delegate* delegate,
-                                      const Extension* extension,
+                                      const extensions::Extension* extension,
                                       const SkBitmap* icon);
 
   // This is called by the installer to verify whether the installation should
   // proceed. This is declared virtual for testing.
   //
   // We *MUST* eventually call either Proceed() or Abort() on |delegate|.
-  virtual void ConfirmInstall(Delegate* delegate, const Extension* extension);
+  virtual void ConfirmInstall(Delegate* delegate,
+                              const extensions::Extension* extension);
 
   // This is called by the app handler launcher to verify whether the app
   // should be re-enabled. This is declared virtual for testing.
   //
   // We *MUST* eventually call either Proceed() or Abort() on |delegate|.
-  virtual void ConfirmReEnable(Delegate* delegate, const Extension* extension);
+  virtual void ConfirmReEnable(Delegate* delegate,
+                               const extensions::Extension* extension);
 
   // This is called by the extension permissions API to verify whether an
   // extension may be granted additional permissions.
   //
   // We *MUST* eventually call either Proceed() or Abort() on |delegate|.
   virtual void ConfirmPermissions(Delegate* delegate,
-                                  const Extension* extension,
+                                  const extensions::Extension* extension,
                                   const ExtensionPermissionSet* permissions);
 
   // Installation was successful. This is declared virtual for testing.
-  virtual void OnInstallSuccess(const Extension* extension, SkBitmap* icon);
+  virtual void OnInstallSuccess(const extensions::Extension* extension,
+                                SkBitmap* icon);
 
   // Installation failed. This is declared virtual for testing.
   virtual void OnInstallFailure(const string16& error);
@@ -235,7 +240,7 @@ class ExtensionInstallUI : public ImageLoadingTracker::Observer {
   // theme.
   static void ShowThemeInfoBar(
       const std::string& previous_theme_id, bool previous_using_native_theme,
-      const Extension* new_theme, Profile* profile);
+      const extensions::Extension* new_theme, Profile* profile);
 
   // Sets the icon that will be used in any UI. If |icon| is NULL, or contains
   // an empty bitmap, then a default icon will be used instead.
@@ -253,7 +258,7 @@ class ExtensionInstallUI : public ImageLoadingTracker::Observer {
   // within its own function due to its platform-specific nature.
   static InfoBarDelegate* GetNewThemeInstalledInfoBarDelegate(
       TabContentsWrapper* tab_contents,
-      const Extension* new_theme,
+      const extensions::Extension* new_theme,
       const std::string& previous_theme_id,
       bool previous_using_native_theme);
 
@@ -268,7 +273,7 @@ class ExtensionInstallUI : public ImageLoadingTracker::Observer {
   SkBitmap icon_;
 
   // The extension we are showing the UI for.
-  const Extension* extension_;
+  const extensions::Extension* extension_;
 
   // The bundle we are showing the UI for, if type BUNDLE_INSTALL_PROMPT.
   const extensions::BundleInstaller* bundle_;
diff --git a/chrome/browser/extensions/extension_install_ui_browsertest.cc b/chrome/browser/extensions/extension_install_ui_browsertest.cc
index 5456236..29415c5 100644
--- a/chrome/browser/extensions/extension_install_ui_browsertest.cc
+++ b/chrome/browser/extensions/extension_install_ui_browsertest.cc
@@ -17,6 +17,7 @@
 #include "content/public/browser/web_contents.h"
 
 using content::WebContents;
+using extensions::Extension;
 
 class ExtensionInstallUIBrowserTest : public ExtensionBrowserTest {
  public:
diff --git a/chrome/browser/extensions/extension_keybinding_apitest.cc b/chrome/browser/extensions/extension_keybinding_apitest.cc
index 69f6dc6..b00097d 100644
--- a/chrome/browser/extensions/extension_keybinding_apitest.cc
+++ b/chrome/browser/extensions/extension_keybinding_apitest.cc
@@ -40,7 +40,7 @@ class KeybindingApiTest : public ExtensionApiTest {
 IN_PROC_BROWSER_TEST_F(KeybindingApiTest, Basic) {
   ASSERT_TRUE(test_server()->Start());
   ASSERT_TRUE(RunExtensionTest("keybinding/basics")) << message_;
-  const Extension* extension = GetSingleLoadedExtension();
+  const extensions::Extension* extension = GetSingleLoadedExtension();
   ASSERT_TRUE(extension) << message_;
 
   // Load this extension, which uses the same keybindings but sets the page
@@ -87,7 +87,7 @@ IN_PROC_BROWSER_TEST_F(KeybindingApiTest, Basic) {
 IN_PROC_BROWSER_TEST_F(KeybindingApiTest, PageAction) {
   ASSERT_TRUE(test_server()->Start());
   ASSERT_TRUE(RunExtensionTest("keybinding/page_action")) << message_;
-  const Extension* extension = GetSingleLoadedExtension();
+  const extensions::Extension* extension = GetSingleLoadedExtension();
   ASSERT_TRUE(extension) << message_;
 
   {
diff --git a/chrome/browser/extensions/extension_keybinding_registry.cc b/chrome/browser/extensions/extension_keybinding_registry.cc
index f05ce51..a985640 100644
--- a/chrome/browser/extensions/extension_keybinding_registry.cc
+++ b/chrome/browser/extensions/extension_keybinding_registry.cc
@@ -47,7 +47,7 @@ void ExtensionKeybindingRegistry::Observe(
   switch (type) {
     case chrome::NOTIFICATION_EXTENSION_LOADED:
       AddExtensionKeybinding(
-          content::Details<const Extension>(details).ptr());
+          content::Details<const extensions::Extension>(details).ptr());
       break;
     case chrome::NOTIFICATION_EXTENSION_UNLOADED:
       RemoveExtensionKeybinding(
diff --git a/chrome/browser/extensions/extension_keybinding_registry.h b/chrome/browser/extensions/extension_keybinding_registry.h
index 0747ce6..39ca0d9 100644
--- a/chrome/browser/extensions/extension_keybinding_registry.h
+++ b/chrome/browser/extensions/extension_keybinding_registry.h
@@ -14,11 +14,12 @@
 #include "content/public/browser/notification_registrar.h"
 #include "content/public/browser/notification_source.h"
 
-class Extension;
 class Profile;
 
 namespace extensions {
 
+class Extension;
+
 // The ExtensionKeybindingRegistry is a class that handles the cross-platform
 // logic for keyboard accelerators. See platform-specific implementations for
 // implementation details for each platform.
@@ -34,9 +35,11 @@ class ExtensionKeybindingRegistry : public content::NotificationObserver {
 
  protected:
   // Add extension keybinding for the events defined by the |extension|.
-  virtual void AddExtensionKeybinding(const Extension* extension) = 0;
+  virtual void AddExtensionKeybinding(
+      const Extension* extension) = 0;
   // Remove extension bindings for |extension|.
-  virtual void RemoveExtensionKeybinding(const Extension* extension) = 0;
+  virtual void RemoveExtensionKeybinding(
+      const Extension* extension) = 0;
 
   // Make sure all extensions registered have keybindings added.
   void Init();
diff --git a/chrome/browser/extensions/extension_management_api.cc b/chrome/browser/extensions/extension_management_api.cc
index fc74f1a..b22ba2f 100644
--- a/chrome/browser/extensions/extension_management_api.cc
+++ b/chrome/browser/extensions/extension_management_api.cc
@@ -40,6 +40,7 @@ using base::IntToString;
 using content::BrowserThread;
 using content::UtilityProcessHost;
 using content::UtilityProcessHostClient;
+using extensions::Extension;
 
 namespace events = extension_event_names;
 namespace keys = extension_management_api_constants;
@@ -489,7 +490,8 @@ void ExtensionManagementEventRouter::Observe(
   } else {
     const Extension* extension = NULL;
     if (event_name == events::kOnExtensionDisabled) {
-      extension = content::Details<UnloadedExtensionInfo>(details)->extension;
+      extension = content::Details<extensions::UnloadedExtensionInfo>(
+          details)->extension;
     } else {
       extension = content::Details<const Extension>(details).ptr();
     }
diff --git a/chrome/browser/extensions/extension_management_browsertest.cc b/chrome/browser/extensions/extension_management_browsertest.cc
index c467491..51e5620 100644
--- a/chrome/browser/extensions/extension_management_browsertest.cc
+++ b/chrome/browser/extensions/extension_management_browsertest.cc
@@ -24,6 +24,8 @@
 #include "content/public/browser/render_view_host.h"
 #include "content/public/common/url_fetcher.h"
 
+using extensions::Extension;
+
 class ExtensionManagementTest : public ExtensionBrowserTest {
  protected:
   // Helper method that returns whether the extension is at the given version.
diff --git a/chrome/browser/extensions/extension_menu_manager.cc b/chrome/browser/extensions/extension_menu_manager.cc
index f0bdca8..5d890de 100644
--- a/chrome/browser/extensions/extension_menu_manager.cc
+++ b/chrome/browser/extensions/extension_menu_manager.cc
@@ -140,8 +140,9 @@ const ExtensionMenuItem::List* ExtensionMenuManager::MenuItems(
   return NULL;
 }
 
-bool ExtensionMenuManager::AddContextItem(const Extension* extension,
-                                          ExtensionMenuItem* item) {
+bool ExtensionMenuManager::AddContextItem(
+    const extensions::Extension* extension,
+    ExtensionMenuItem* item) {
   const std::string& extension_id = item->extension_id();
   // The item must have a non-empty extension id, and not have already been
   // added.
@@ -544,8 +545,8 @@ void ExtensionMenuManager::Observe(
   DCHECK(type == chrome::NOTIFICATION_EXTENSION_UNLOADED);
 
   // Remove menu items for disabled/uninstalled extensions.
-  const Extension* extension =
-      content::Details<UnloadedExtensionInfo>(details)->extension;
+  const extensions::Extension* extension =
+      content::Details<extensions::UnloadedExtensionInfo>(details)->extension;
   if (ContainsKey(context_items_, extension->id())) {
     RemoveAllContextItems(extension->id());
   }
diff --git a/chrome/browser/extensions/extension_menu_manager.h b/chrome/browser/extensions/extension_menu_manager.h
index 30a8b35..1235bdb 100644
--- a/chrome/browser/extensions/extension_menu_manager.h
+++ b/chrome/browser/extensions/extension_menu_manager.h
@@ -22,7 +22,6 @@
 #include "content/public/browser/notification_registrar.h"
 
 
-class Extension;
 class Profile;
 class SkBitmap;
 
@@ -31,6 +30,10 @@ class WebContents;
 struct ContextMenuParams;
 }
 
+namespace extensions {
+class Extension;
+}
+
 // Represents a menu item added by an extension.
 class ExtensionMenuItem {
  public:
@@ -224,7 +227,8 @@ class ExtensionMenuManager : public content::NotificationObserver {
   // Adds a top-level menu item for an extension, requiring the |extension|
   // pointer so it can load the icon for the extension. Takes ownership of
   // |item|. Returns a boolean indicating success or failure.
-  bool AddContextItem(const Extension* extension, ExtensionMenuItem* item);
+  bool AddContextItem(const extensions::Extension* extension,
+                      ExtensionMenuItem* item);
 
   // Add an item as a child of another item which has been previously added, and
   // takes ownership of |item|. Returns a boolean indicating success or failure.
diff --git a/chrome/browser/extensions/extension_menu_manager_unittest.cc b/chrome/browser/extensions/extension_menu_manager_unittest.cc
index a506545..7862ec5 100644
--- a/chrome/browser/extensions/extension_menu_manager_unittest.cc
+++ b/chrome/browser/extensions/extension_menu_manager_unittest.cc
@@ -26,6 +26,7 @@
 #include "testing/gtest/include/gtest/gtest.h"
 
 using content::BrowserThread;
+using extensions::Extension;
 using testing::_;
 using testing::AtLeast;
 using testing::Return;
@@ -75,7 +76,7 @@ class ExtensionMenuManagerTest : public testing::Test {
   content::TestBrowserThread file_thread_;
 
   ExtensionMenuManager manager_;
-  ExtensionList extensions_;
+  extensions::ExtensionList extensions_;
   TestExtensionPrefs prefs_;
   int next_id_;
 
@@ -357,11 +358,12 @@ TEST_F(ExtensionMenuManagerTest, ExtensionUnloadRemovesMenuItems) {
 
   // Notify that the extension was unloaded, and make sure the right item is
   // gone.
-  UnloadedExtensionInfo details(
+  extensions::UnloadedExtensionInfo details(
       extension1, extension_misc::UNLOAD_REASON_DISABLE);
   notifier->Notify(chrome::NOTIFICATION_EXTENSION_UNLOADED,
                    content::Source<Profile>(&profile_),
-                   content::Details<UnloadedExtensionInfo>(&details));
+                   content::Details<extensions::UnloadedExtensionInfo>(
+                      &details));
   ASSERT_EQ(NULL, manager_.MenuItems(extension1->id()));
   ASSERT_EQ(1u, manager_.MenuItems(extension2->id())->size());
   ASSERT_TRUE(manager_.GetItemById(id1) == NULL);
diff --git a/chrome/browser/extensions/extension_message_service.cc b/chrome/browser/extensions/extension_message_service.cc
index d041527..c522eaf 100644
--- a/chrome/browser/extensions/extension_message_service.cc
+++ b/chrome/browser/extensions/extension_message_service.cc
@@ -126,7 +126,7 @@ static content::RenderProcessHost* GetExtensionProcess(
     Profile* profile, const std::string& extension_id) {
   SiteInstance* site_instance =
       profile->GetExtensionProcessManager()->GetSiteInstanceForURL(
-          Extension::GetBaseURLFromExtensionId(extension_id));
+          extensions::Extension::GetBaseURLFromExtensionId(extension_id));
 
   if (!site_instance->HasProcess())
     return NULL;
@@ -430,7 +430,8 @@ bool ExtensionMessageService::MaybeAddPendingOpenChannelTask(
     const OpenChannelParams& params) {
   ExtensionService* service = profile->GetExtensionService();
   const std::string& extension_id = params.target_extension_id;
-  const Extension* extension = service->extensions()->GetByID(extension_id);
+  const extensions::Extension* extension = service->extensions()->GetByID(
+      extension_id);
   if (extension && extension->has_lazy_background_page()) {
     // If the extension uses spanning incognito mode, make sure we're always
     // using the original profile since that is what the extension process
diff --git a/chrome/browser/extensions/extension_module.cc b/chrome/browser/extensions/extension_module.cc
index f09de0b..cd35b42 100644
--- a/chrome/browser/extensions/extension_module.cc
+++ b/chrome/browser/extensions/extension_module.cc
@@ -24,7 +24,7 @@ bool SetUpdateUrlDataFunction::RunImpl() {
 
 bool IsAllowedIncognitoAccessFunction::RunImpl() {
   ExtensionService* ext_service = profile()->GetExtensionService();
-  const Extension* extension = GetExtension();
+  const extensions::Extension* extension = GetExtension();
 
   result_.reset(Value::CreateBooleanValue(
       ext_service->IsIncognitoEnabled(extension->id())));
@@ -33,7 +33,7 @@ bool IsAllowedIncognitoAccessFunction::RunImpl() {
 
 bool IsAllowedFileSchemeAccessFunction::RunImpl() {
   ExtensionService* ext_service = profile()->GetExtensionService();
-  const Extension* extension = GetExtension();
+  const extensions::Extension* extension = GetExtension();
 
   result_.reset(Value::CreateBooleanValue(
         ext_service->AllowFileAccess(extension)));
diff --git a/chrome/browser/extensions/extension_nacl_browsertest.cc b/chrome/browser/extensions/extension_nacl_browsertest.cc
index 8565d8d..58ccfbb 100644
--- a/chrome/browser/extensions/extension_nacl_browsertest.cc
+++ b/chrome/browser/extensions/extension_nacl_browsertest.cc
@@ -22,6 +22,7 @@
 
 using content::PluginService;
 using content::WebContents;
+using extensions::Extension;
 
 namespace {
 
diff --git a/chrome/browser/extensions/extension_navigation_observer.cc b/chrome/browser/extensions/extension_navigation_observer.cc
index d827f80..2cb1bc6 100644
--- a/chrome/browser/extensions/extension_navigation_observer.cc
+++ b/chrome/browser/extensions/extension_navigation_observer.cc
@@ -55,7 +55,7 @@ void ExtensionNavigationObserver::PromptToEnableExtensionIfNecessary(
     return;
 
   ExtensionService* extension_service = profile_->GetExtensionService();
-  const Extension* extension =
+  const extensions::Extension* extension =
       extension_service->disabled_extensions()->
       GetExtensionOrAppByURL(ExtensionURLInfo(nav_entry->GetURL()));
   if (!extension)
@@ -80,7 +80,7 @@ void ExtensionNavigationObserver::PromptToEnableExtensionIfNecessary(
 
 void ExtensionNavigationObserver::InstallUIProceed() {
   ExtensionService* extension_service = profile_->GetExtensionService();
-  const Extension* extension = extension_service->GetExtensionById(
+  const extensions::Extension* extension = extension_service->GetExtensionById(
       in_progress_prompt_extension_id_, true);
   NavigationController* nav_controller =
       in_progress_prompt_navigation_controller_;
@@ -98,7 +98,7 @@ void ExtensionNavigationObserver::InstallUIProceed() {
 
 void ExtensionNavigationObserver::InstallUIAbort(bool user_initiated) {
   ExtensionService* extension_service = profile_->GetExtensionService();
-  const Extension* extension = extension_service->GetExtensionById(
+  const extensions::Extension* extension = extension_service->GetExtensionById(
       in_progress_prompt_extension_id_, true);
 
   in_progress_prompt_extension_id_ = "";
diff --git a/chrome/browser/extensions/extension_override_apitest.cc b/chrome/browser/extensions/extension_override_apitest.cc
index 50d59c5..fd63acd 100644
--- a/chrome/browser/extensions/extension_override_apitest.cc
+++ b/chrome/browser/extensions/extension_override_apitest.cc
@@ -117,7 +117,7 @@ IN_PROC_BROWSER_TEST_F(ExtensionOverrideTest, MAYBE_OverrideHistory) {
 
 // Regression test for http://crbug.com/41442.
 IN_PROC_BROWSER_TEST_F(ExtensionOverrideTest, ShouldNotCreateDuplicateEntries) {
-  const Extension* extension =
+  const extensions::Extension* extension =
       LoadExtension(test_data_dir_.AppendASCII("override/history"));
   ASSERT_TRUE(extension);
 
@@ -164,7 +164,7 @@ IN_PROC_BROWSER_TEST_F(ExtensionOverrideTest, OverrideKeyboard) {
   }
 
   // Load the failing version.  This should take precedence.
-  const Extension* extension = LoadExtension(
+  const extensions::Extension* extension = LoadExtension(
       test_data_dir_.AppendASCII("override").AppendASCII("keyboard_fails"));
   ASSERT_TRUE(extension);
   {
diff --git a/chrome/browser/extensions/extension_prefs.cc b/chrome/browser/extensions/extension_prefs.cc
index 5fb0bb4..faf3bd5 100644
--- a/chrome/browser/extensions/extension_prefs.cc
+++ b/chrome/browser/extensions/extension_prefs.cc
@@ -22,6 +22,9 @@
 #include "chrome/common/url_constants.h"
 #include "content/public/browser/notification_service.h"
 
+using extensions::Extension;
+using extensions::ExtensionInfo;
+
 namespace {
 
 // Additional preferences keys
@@ -855,8 +858,8 @@ void ExtensionPrefs::SetActiveBit(const std::string& extension_id,
 
 void ExtensionPrefs::MigratePermissions(const ExtensionIdSet& extension_ids) {
   ExtensionPermissionsInfo* info = ExtensionPermissionsInfo::GetInstance();
-  for (ExtensionIdSet::const_iterator ext_id = extension_ids.begin();
-       ext_id != extension_ids.end(); ++ext_id) {
+  for (ExtensionIdSet::const_iterator ext_id =
+       extension_ids.begin(); ext_id != extension_ids.end(); ++ext_id) {
 
     // An extension's granted permissions need to be migrated if the
     // full_access bit is present. This bit was always present in the previous
@@ -1166,7 +1169,7 @@ bool ExtensionPrefs::IsExtensionDisabled(
 }
 
 std::vector<std::string> ExtensionPrefs::GetToolbarOrder() {
-  ExtensionPrefs::ExtensionIdSet extension_ids;
+  ExtensionIdSet extension_ids;
   const ListValue* toolbar_order = prefs_->GetList(kExtensionToolbar);
   if (toolbar_order) {
     for (size_t i = 0; i < toolbar_order->GetSize(); ++i) {
diff --git a/chrome/browser/extensions/extension_prefs.h b/chrome/browser/extensions/extension_prefs.h
index 31bf160..adfb45f 100644
--- a/chrome/browser/extensions/extension_prefs.h
+++ b/chrome/browser/extensions/extension_prefs.h
@@ -52,7 +52,7 @@ class ExtensionPrefs : public extensions::ContentSettingsStore::Observer,
   // extension ids.
   static const char kExtensionsPref[];
 
-  typedef std::vector<linked_ptr<ExtensionInfo> > ExtensionsInfo;
+  typedef std::vector<linked_ptr<extensions::ExtensionInfo> > ExtensionsInfo;
 
   // Vector containing identifiers for preferences.
   typedef std::set<std::string> PrefKeySet;
@@ -110,18 +110,19 @@ class ExtensionPrefs : public extensions::ContentSettingsStore::Observer,
   // Called when an extension is installed, so that prefs get created.
   // If |page_ordinal| is an invalid ordinal, then a page will be found
   // for the App.
-  void OnExtensionInstalled(const Extension* extension,
-                            Extension::State initial_state,
+  void OnExtensionInstalled(const extensions::Extension* extension,
+                            extensions::Extension::State initial_state,
                             bool from_webstore,
                             const StringOrdinal& page_ordinal);
 
   // Called when an extension is uninstalled, so that prefs get cleaned up.
   void OnExtensionUninstalled(const std::string& extension_id,
-                              const Extension::Location& location,
+                              const extensions::Extension::Location& location,
                               bool external_uninstall);
 
   // Called to change the extension's state when it is enabled/disabled.
-  void SetExtensionState(const std::string& extension_id, Extension::State);
+  void SetExtensionState(const std::string& extension_id,
+      extensions::Extension::State);
 
   // Returns all installed extensions
   void GetExtensions(ExtensionIdSet* out);
@@ -133,21 +134,24 @@ class ExtensionPrefs : public extensions::ContentSettingsStore::Observer,
       const base::DictionaryValue* extension_prefs);
 
   // Getter and setter for browser action visibility.
-  bool GetBrowserActionVisibility(const Extension* extension);
-  void SetBrowserActionVisibility(const Extension* extension, bool visible);
+  bool GetBrowserActionVisibility(const extensions::Extension* extension);
+  void SetBrowserActionVisibility(const extensions::Extension* extension,
+     bool visible);
 
   // Did the extension ask to escalate its permission during an upgrade?
   bool DidExtensionEscalatePermissions(const std::string& id);
 
   // If |did_escalate| is true, the preferences for |extension| will be set to
   // require the install warning when the user tries to enable.
-  void SetDidExtensionEscalatePermissions(const Extension* extension,
-                                          bool did_escalate);
+  void SetDidExtensionEscalatePermissions(
+      const extensions::Extension* extension,
+      bool did_escalate);
 
   // Getter and setters for disabled reason.
-  Extension::DisableReason GetDisableReason(const std::string& extension_id);
+  extensions::Extension::DisableReason GetDisableReason(
+      const std::string& extension_id);
   void SetDisableReason(const std::string& extension_id,
-                        Extension::DisableReason disable_reason);
+                        extensions::Extension::DisableReason disable_reason);
   void RemoveDisableReason(const std::string& extension_id);
 
   // Returns the version string for the currently installed extension, or
@@ -156,7 +160,7 @@ class ExtensionPrefs : public extensions::ContentSettingsStore::Observer,
 
   // Re-writes the extension manifest into the prefs.
   // Called to change the extension's manifest when it's re-localized.
-  void UpdateManifest(const Extension* extension);
+  void UpdateManifest(const extensions::Extension* extension);
 
   // Returns extension path based on extension ID, or empty FilePath on error.
   FilePath GetExtensionPath(const std::string& extension_id);
@@ -205,7 +209,7 @@ class ExtensionPrefs : public extensions::ContentSettingsStore::Observer,
   // Is the extension with |extension_id| allowed by policy (checking both
   // whitelist and blacklist).
   bool IsExtensionAllowedByPolicy(const std::string& extension_id,
-                                  Extension::Location location) const;
+      extensions::Extension::Location location) const;
 
   // Checks if extensions are blacklisted by default, by policy. When true, this
   // means that even extensions without an ID should be blacklisted (e.g.
@@ -301,7 +305,7 @@ class ExtensionPrefs : public extensions::ContentSettingsStore::Observer,
   // If |extension|'s prefs do not have a launch type set, then
   // use |default_pref_value|.
   extension_misc::LaunchContainer GetLaunchContainer(
-      const Extension* extension,
+      const extensions::Extension* extension,
       LaunchType default_pref_value);
 
   // Saves ExtensionInfo for each installed extension with the path to the
@@ -312,7 +316,8 @@ class ExtensionPrefs : public extensions::ContentSettingsStore::Observer,
 
   // Returns the ExtensionInfo from the prefs for the given extension. If the
   // extension is not present, NULL is returned.
-  ExtensionInfo* GetInstalledExtensionInfo(const std::string& extension_id);
+  extensions::ExtensionInfo* GetInstalledExtensionInfo(
+      const std::string& extension_id);
 
   // We've downloaded an updated .crx file for the extension, but are waiting
   // for idle time to install it.
@@ -522,7 +527,7 @@ class ExtensionPrefs : public extensions::ContentSettingsStore::Observer,
   // Checks whether there is a state pref for the extension and if so, whether
   // it matches |check_state|.
   bool DoesExtensionHaveState(const std::string& id,
-                              Extension::State check_state) const;
+                              extensions::Extension::State check_state) const;
 
   // The pref service specific to this set of extension prefs. Owned by profile.
   PrefService* prefs_;
diff --git a/chrome/browser/extensions/extension_prefs_unittest.cc b/chrome/browser/extensions/extension_prefs_unittest.cc
index 17bb3b1..378dfbf 100644
--- a/chrome/browser/extensions/extension_prefs_unittest.cc
+++ b/chrome/browser/extensions/extension_prefs_unittest.cc
@@ -25,6 +25,8 @@
 using base::Time;
 using base::TimeDelta;
 using content::BrowserThread;
+using extensions::Extension;
+using extensions::ExtensionList;
 
 namespace {
 
@@ -447,7 +449,7 @@ class ExtensionPrefsBlacklist : public ExtensionPrefsTest {
     EXPECT_EQ(4u, info->size());
     ExtensionPrefs::ExtensionsInfo::iterator info_iter;
     for (info_iter = info->begin(); info_iter != info->end(); ++info_iter) {
-      ExtensionInfo* extension_info = info_iter->get();
+      extensions::ExtensionInfo* extension_info = info_iter->get();
       EXPECT_NE(extensions_[0]->id(), extension_info->extension_id);
     }
   }
diff --git a/chrome/browser/extensions/extension_prefs_unittest.h b/chrome/browser/extensions/extension_prefs_unittest.h
index bda1dca..7a97651 100644
--- a/chrome/browser/extensions/extension_prefs_unittest.h
+++ b/chrome/browser/extensions/extension_prefs_unittest.h
@@ -15,6 +15,10 @@ namespace base {
 class Value;
 }
 
+namespace extensions {
+class Extension;
+}
+
 // Base class for extension preference-related unit tests.
 class ExtensionPrefsTest : public testing::Test {
  public:
@@ -57,41 +61,41 @@ class ExtensionPrefsPrepopulatedTest : public ExtensionPrefsTest {
 
   virtual void RegisterPreferences() OVERRIDE;
 
-  void InstallExtControlledPref(Extension *ext,
+  void InstallExtControlledPref(extensions::Extension* ext,
                                 const std::string& key,
                                 base::Value* val);
 
-  void InstallExtControlledPrefIncognito(Extension *ext,
+  void InstallExtControlledPrefIncognito(extensions::Extension* ext,
                                          const std::string& key,
                                          base::Value* val);
 
   void InstallExtControlledPrefIncognitoSessionOnly(
-      Extension *ext,
+      extensions::Extension* ext,
       const std::string& key,
       base::Value* val);
 
-  void InstallExtension(Extension *ext);
+  void InstallExtension(extensions::Extension* ext);
 
   void UninstallExtension(const std::string& extension_id);
 
   // Weak references, for convenience.
-  Extension* ext1_;
-  Extension* ext2_;
-  Extension* ext3_;
-  Extension* ext4_;
+  extensions::Extension* ext1_;
+  extensions::Extension* ext2_;
+  extensions::Extension* ext3_;
+  extensions::Extension* ext4_;
 
   // Flags indicating whether each of the extensions has been installed, yet.
   bool installed[4];
 
  private:
-  void EnsureExtensionInstalled(Extension *ext);
+  void EnsureExtensionInstalled(extensions::Extension *ext);
 
   void EnsureExtensionUninstalled(const std::string& extension_id);
 
-  scoped_refptr<Extension> ext1_scoped_;
-  scoped_refptr<Extension> ext2_scoped_;
-  scoped_refptr<Extension> ext3_scoped_;
-  scoped_refptr<Extension> ext4_scoped_;
+  scoped_refptr<extensions::Extension> ext1_scoped_;
+  scoped_refptr<extensions::Extension> ext2_scoped_;
+  scoped_refptr<extensions::Extension> ext3_scoped_;
+  scoped_refptr<extensions::Extension> ext4_scoped_;
 };
 
 
diff --git a/chrome/browser/extensions/extension_process_manager.cc b/chrome/browser/extensions/extension_process_manager.cc
index 63437bd..1685138 100644
--- a/chrome/browser/extensions/extension_process_manager.cc
+++ b/chrome/browser/extensions/extension_process_manager.cc
@@ -43,6 +43,7 @@ using content::OpenURLParams;
 using content::Referrer;
 using content::RenderViewHost;
 using content::SiteInstance;
+using extensions::Extension;
 
 namespace {
 
@@ -540,7 +541,8 @@ void ExtensionProcessManager::Observe(
 
     case chrome::NOTIFICATION_EXTENSION_UNLOADED: {
       const Extension* extension =
-          content::Details<UnloadedExtensionInfo>(details)->extension;
+          content::Details<extensions::UnloadedExtensionInfo>(
+              details)->extension;
       for (ExtensionHostSet::iterator iter = background_hosts_.begin();
            iter != background_hosts_.end(); ++iter) {
         ExtensionHost* host = *iter;
diff --git a/chrome/browser/extensions/extension_process_manager.h b/chrome/browser/extensions/extension_process_manager.h
index 33f5820..c695d21 100644
--- a/chrome/browser/extensions/extension_process_manager.h
+++ b/chrome/browser/extensions/extension_process_manager.h
@@ -19,7 +19,6 @@
 #include "content/public/browser/notification_registrar.h"
 
 class Browser;
-class Extension;
 class ExtensionHost;
 class GURL;
 class Profile;
@@ -29,6 +28,10 @@ class RenderViewHost;
 class SiteInstance;
 };
 
+namespace extensions {
+class Extension;
+}
+
 // Manages dynamic state of running Chromium extensions. There is one instance
 // of this class per Profile. OTR Profiles have a separate instance that keeps
 // track of split-mode extensions only.
@@ -50,30 +53,31 @@ class ExtensionProcessManager : public content::NotificationObserver {
   // Creates a new ExtensionHost with its associated view, grouping it in the
   // appropriate SiteInstance (and therefore process) based on the URL and
   // profile.
-  virtual ExtensionHost* CreateViewHost(const Extension* extension,
+  virtual ExtensionHost* CreateViewHost(const extensions::Extension* extension,
                                         const GURL& url,
                                         Browser* browser,
                                         content::ViewType view_type);
   ExtensionHost* CreateViewHost(const GURL& url,
                                 Browser* browser,
                                 content::ViewType view_type);
-  ExtensionHost* CreatePopupHost(const Extension* extension,
+  ExtensionHost* CreatePopupHost(const extensions::Extension* extension,
                                  const GURL& url,
                                  Browser* browser);
   ExtensionHost* CreatePopupHost(const GURL& url, Browser* browser);
   ExtensionHost* CreateDialogHost(const GURL& url, Browser* browser);
-  ExtensionHost* CreateInfobarHost(const Extension* extension,
+  ExtensionHost* CreateInfobarHost(const extensions::Extension* extension,
                                    const GURL& url,
                                    Browser* browser);
   ExtensionHost* CreateInfobarHost(const GURL& url,
                                    Browser* browser);
 
   // Open the extension's options page.
-  void OpenOptionsPage(const Extension* extension, Browser* browser);
+  void OpenOptionsPage(const extensions::Extension* extension,
+                       Browser* browser);
 
   // Creates a new UI-less extension instance.  Like CreateViewHost, but not
   // displayed anywhere.
-  virtual void CreateBackgroundHost(const Extension* extension,
+  virtual void CreateBackgroundHost(const extensions::Extension* extension,
                                     const GURL& url);
 
   // Gets the ExtensionHost for the background page for an extension, or NULL if
@@ -87,7 +91,7 @@ class ExtensionProcessManager : public content::NotificationObserver {
 
   // Registers a RenderViewHost as hosting a given extension.
   void RegisterRenderViewHost(content::RenderViewHost* render_view_host,
-                              const Extension* extension);
+                              const extensions::Extension* extension);
 
   // Unregisters a RenderViewHost as hosting any extension.
   void UnregisterRenderViewHost(content::RenderViewHost* render_view_host);
@@ -99,7 +103,7 @@ class ExtensionProcessManager : public content::NotificationObserver {
 
   // Returns the extension associated with the specified RenderViewHost, or
   // NULL.
-  const Extension* GetExtensionForRenderViewHost(
+  const extensions::Extension* GetExtensionForRenderViewHost(
       content::RenderViewHost* render_view_host);
 
   // Returns true if the (lazy) background host for the given extension has
@@ -110,9 +114,9 @@ class ExtensionProcessManager : public content::NotificationObserver {
   // the count of how many outstanding "things" are keeping the page alive.
   // When this reaches 0, we will begin the process of shutting down the page.
   // "Things" include pending events, resource loads, and API calls.
-  int GetLazyKeepaliveCount(const Extension* extension);
-  int IncrementLazyKeepaliveCount(const Extension* extension);
-  int DecrementLazyKeepaliveCount(const Extension* extension);
+  int GetLazyKeepaliveCount(const extensions::Extension* extension);
+  int IncrementLazyKeepaliveCount(const extensions::Extension* extension);
+  int DecrementLazyKeepaliveCount(const extensions::Extension* extension);
 
   void IncrementLazyKeepaliveCountForView(
       content::RenderViewHost* render_view_host);
diff --git a/chrome/browser/extensions/extension_protocols.cc b/chrome/browser/extensions/extension_protocols.cc
index 67e92a7..bf836bb 100644
--- a/chrome/browser/extensions/extension_protocols.cc
+++ b/chrome/browser/extensions/extension_protocols.cc
@@ -35,6 +35,7 @@
 #include "ui/base/resource/resource_bundle.h"
 
 using content::ResourceRequestInfo;
+using extensions::Extension;
 
 namespace {
 
diff --git a/chrome/browser/extensions/extension_protocols_unittest.cc b/chrome/browser/extensions/extension_protocols_unittest.cc
index 2437db4..6c0f96b 100644
--- a/chrome/browser/extensions/extension_protocols_unittest.cc
+++ b/chrome/browser/extensions/extension_protocols_unittest.cc
@@ -18,6 +18,7 @@
 #include "testing/gtest/include/gtest/gtest.h"
 
 using content::BrowserThread;
+using extensions::Extension;
 
 namespace {
 
diff --git a/chrome/browser/extensions/extension_service.cc b/chrome/browser/extensions/extension_service.cc
index bb0f44a..9a50210 100644
--- a/chrome/browser/extensions/extension_service.cc
+++ b/chrome/browser/extensions/extension_service.cc
@@ -133,6 +133,10 @@ using content::BrowserThread;
 using content::DevToolsAgentHost;
 using content::DevToolsAgentHostRegistry;
 using content::PluginService;
+using extensions::Extension;
+using extensions::ExtensionIdSet;
+using extensions::ExtensionInfo;
+using extensions::UnloadedExtensionInfo;
 
 namespace errors = extension_manifest_errors;
 
diff --git a/chrome/browser/extensions/extension_service.h b/chrome/browser/extensions/extension_service.h
index d774113..01e056d 100644
--- a/chrome/browser/extensions/extension_service.h
+++ b/chrome/browser/extensions/extension_service.h
@@ -78,6 +78,7 @@ class APIResourceController;
 class AppSyncData;
 class ComponentLoader;
 class ContentSettingsStore;
+class Extension;
 class ExtensionCookiesEventRouter;
 class ExtensionSyncData;
 class ExtensionUpdater;
@@ -92,7 +93,7 @@ class ExtensionServiceInterface : public SyncableService {
   // A function that returns true if the given extension should be
   // included and false if it should be filtered out.  Identical to
   // PendingExtensionInfo::ShouldAllowInstallPredicate.
-  typedef bool (*ExtensionFilter)(const Extension&);
+  typedef bool (*ExtensionFilter)(const extensions::Extension&);
 
   virtual ~ExtensionServiceInterface() {}
   virtual const ExtensionSet* extensions() const = 0;
@@ -106,9 +107,9 @@ class ExtensionServiceInterface : public SyncableService {
       const FilePath& path,
       const GURL& download_url,
       CrxInstaller** out_crx_installer) = 0;
-  virtual const Extension* GetExtensionById(const std::string& id,
+  virtual const extensions::Extension* GetExtensionById(const std::string& id,
                                             bool include_disabled) const = 0;
-  virtual const Extension* GetInstalledExtension(
+  virtual const extensions::Extension* GetInstalledExtension(
       const std::string& id) const = 0;
 
   virtual bool IsExtensionEnabled(const std::string& extension_id) const = 0;
@@ -125,13 +126,14 @@ class ExtensionServiceInterface : public SyncableService {
   // themes sync to not use it directly.
   virtual void CheckForUpdatesSoon() = 0;
 
-  virtual void AddExtension(const Extension* extension) = 0;
+  virtual void AddExtension(const extensions::Extension* extension) = 0;
 
   virtual void UnloadExtension(
       const std::string& extension_id,
       extension_misc::UnloadedExtensionReason reason) = 0;
 
-  virtual void SyncExtensionChangeIfNeeded(const Extension& extension) = 0;
+  virtual void SyncExtensionChangeIfNeeded(
+      const extensions::Extension& extension) = 0;
 
   virtual bool is_ready() = 0;
 };
@@ -169,17 +171,19 @@ class ExtensionService
   static const char* kSyncExtensionSettingsDirectoryName;
 
   // Returns the Extension of hosted or packaged apps, NULL otherwise.
-  const Extension* GetInstalledApp(const GURL& url);
+  const extensions::Extension* GetInstalledApp(const GURL& url);
 
   // Returns whether the URL is from either a hosted or packaged app.
   bool IsInstalledApp(const GURL& url);
 
   // Associates a renderer process with the given installed app.
-  void SetInstalledAppForRenderer(int renderer_child_id, const Extension* app);
+  void SetInstalledAppForRenderer(int renderer_child_id,
+      const extensions::Extension* app);
 
   // If the renderer is hosting an installed app, returns it, otherwise returns
   // NULL.
-  const Extension* GetInstalledAppForRenderer(int renderer_child_id);
+  const extensions::Extension* GetInstalledAppForRenderer(
+      int renderer_child_id);
 
   // Attempts to uninstall an extension from a given ExtensionService. Returns
   // true iff the target extension exists.
@@ -239,36 +243,36 @@ class ExtensionService
 
   // Returns true if the given extension can see events and data from another
   // sub-profile (incognito to original profile, or vice versa).
-  bool CanCrossIncognito(const Extension* extension);
+  bool CanCrossIncognito(const extensions::Extension* extension);
 
   // Returns true if the given extension can be loaded in incognito.
-  bool CanLoadInIncognito(const Extension* extension) const;
+  bool CanLoadInIncognito(const extensions::Extension* extension) const;
 
   // Whether this extension can inject scripts into pages with file URLs.
-  bool AllowFileAccess(const Extension* extension);
+  bool AllowFileAccess(const extensions::Extension* extension);
   // Will reload the extension since this permission is applied at loading time
   // only.
-  void SetAllowFileAccess(const Extension* extension, bool allow);
+  void SetAllowFileAccess(const extensions::Extension* extension, bool allow);
 
   // Whether the persistent background page, if any, is ready. We don't load
   // other components until then. If there is no background page, or if it is
   // non-persistent (lazy), we consider it to be ready.
-  bool IsBackgroundPageReady(const Extension* extension);
-  void SetBackgroundPageReady(const Extension* extension);
+  bool IsBackgroundPageReady(const extensions::Extension* extension);
+  void SetBackgroundPageReady(const extensions::Extension* extension);
 
   // Getter and setter for the flag that specifies whether the extension is
   // being upgraded.
-  bool IsBeingUpgraded(const Extension* extension);
-  void SetBeingUpgraded(const Extension* extension, bool value);
+  bool IsBeingUpgraded(const extensions::Extension* extension);
+  void SetBeingUpgraded(const extensions::Extension* extension, bool value);
 
   // Getter and setter for the flag that specifies if the extension has used
   // the webrequest API.
   // TODO(mpcomplete): remove. http://crbug.com/100411
-  bool HasUsedWebRequest(const Extension* extension);
-  void SetHasUsedWebRequest(const Extension* extension, bool value);
+  bool HasUsedWebRequest(const extensions::Extension* extension);
+  void SetHasUsedWebRequest(const extensions::Extension* extension, bool value);
 
   // Getter for the extension's runtime data PropertyBag.
-  base::PropertyBag* GetPropertyBag(const Extension* extension);
+  base::PropertyBag* GetPropertyBag(const extensions::Extension* extension);
 
   // Initialize and start all installed extensions.
   void Init();
@@ -287,15 +291,16 @@ class ExtensionService
 
   // Look up an extension by ID.  Does not include terminated
   // extensions.
-  virtual const Extension* GetExtensionById(
+  virtual const extensions::Extension* GetExtensionById(
       const std::string& id, bool include_disabled) const OVERRIDE;
 
   // Looks up a terminated (crashed) extension by ID.
-  const Extension* GetTerminatedExtension(const std::string& id) const;
+  const extensions::Extension*
+      GetTerminatedExtension(const std::string& id) const;
 
   // Looks up an extension by ID, regardless of whether it's enabled,
   // disabled, or terminated.
-  virtual const Extension* GetInstalledExtension(
+  virtual const extensions::Extension* GetInstalledExtension(
       const std::string& id) const OVERRIDE;
 
   // Updates a currently-installed extension with the contents from
@@ -338,12 +343,13 @@ class ExtensionService
   // Disables the extension.  If the extension is already disabled, or
   // cannot be disabled, does nothing.
   virtual void DisableExtension(const std::string& extension_id,
-                                Extension::DisableReason disable_reason);
+      extensions::Extension::DisableReason disable_reason);
 
   // Updates the |extension|'s granted permissions lists to include all
   // permissions in the |extension|'s manifest and re-enables the
   // extension.
-  void GrantPermissionsAndEnableExtension(const Extension* extension);
+  void GrantPermissionsAndEnableExtension(
+      const extensions::Extension* extension);
 
   // Check for updates (or potentially new extensions from external providers)
   void CheckForExternalUpdates();
@@ -365,7 +371,8 @@ class ExtensionService
 
   // Notifies Sync (if needed) of a newly-installed extension or a change to
   // an existing extension.
-  virtual void SyncExtensionChangeIfNeeded(const Extension& extension) OVERRIDE;
+  virtual void SyncExtensionChangeIfNeeded(
+      const extensions::Extension& extension) OVERRIDE;
 
   // Returns true if |url| should get extension api bindings and be permitted
   // to make api calls. Note that this is independent of what extension
@@ -385,17 +392,17 @@ class ExtensionService
   // Adds |extension| to this ExtensionService and notifies observers than an
   // extension has been loaded.  Called by the backend after an extension has
   // been loaded from a file and installed.
-  virtual void AddExtension(const Extension* extension) OVERRIDE;
+  virtual void AddExtension(const extensions::Extension* extension) OVERRIDE;
 
   // Called by the backend when an extension has been installed.
   void OnExtensionInstalled(
-      const Extension* extension,
+      const extensions::Extension* extension,
       bool from_webstore,
       const StringOrdinal& page_ordinal);
 
   // Initializes the |extension|'s active permission set and disables the
   // extension if the privilege level has increased (e.g., due to an upgrade).
-  void InitializePermissions(const Extension* extension);
+  void InitializePermissions(const extensions::Extension* extension);
 
   // Go through each extensions in pref, unload blacklisted extensions
   // and update the blacklist state in pref.
@@ -424,11 +431,12 @@ class ExtensionService
   // Gets the sync data for the given extension, assuming that the extension is
   // syncable.
   extensions::ExtensionSyncData GetExtensionSyncData(
-      const Extension& extension) const;
+      const extensions::Extension& extension) const;
 
   // Gets the sync data for the given app, assuming that the app is
   // syncable.
-  extensions::AppSyncData GetAppSyncData(const Extension& extension) const;
+  extensions::AppSyncData GetAppSyncData(
+      const extensions::Extension& extension) const;
 
   // Gets the ExtensionSyncData for all extensions.
   std::vector<extensions::ExtensionSyncData> GetExtensionSyncDataList() const;
@@ -524,18 +532,18 @@ class ExtensionService
   void AddProviderForTesting(ExternalExtensionProviderInterface* test_provider);
 
   // ExternalExtensionProvider::Visitor implementation.
-  virtual bool OnExternalExtensionFileFound(const std::string& id,
-                                            const Version* version,
-                                            const FilePath& path,
-                                            Extension::Location location,
-                                            int creation_flags,
-                                            bool mark_acknowledged)
-      OVERRIDE;
-
-  virtual bool OnExternalExtensionUpdateUrlFound(const std::string& id,
-                                                 const GURL& update_url,
-                                                 Extension::Location location)
-      OVERRIDE;
+  virtual bool OnExternalExtensionFileFound(
+      const std::string& id,
+      const Version* version,
+      const FilePath& path,
+      extensions::Extension::Location location,
+      int creation_flags,
+      bool mark_acknowledged) OVERRIDE;
+
+  virtual bool OnExternalExtensionUpdateUrlFound(
+      const std::string& id,
+      const GURL& update_url,
+      extensions::Extension::Location location) OVERRIDE;
 
   virtual void OnExternalProviderReady(
       const ExternalExtensionProviderInterface* provider) OVERRIDE;
@@ -581,17 +589,17 @@ class ExtensionService
   bool HasApps() const;
 
   // Gets the set of loaded app ids. Component apps are not included.
-  ExtensionIdSet GetAppIds() const;
+  extensions::ExtensionIdSet GetAppIds() const;
 
   // Record a histogram using the PermissionMessage enum values for each
   // permission in |e|.
   // NOTE: If this is ever called with high frequency, the implementation may
   // need to be made more efficient.
   static void RecordPermissionMessagesHistogram(
-      const Extension* e, const char* histogram);
+      const extensions::Extension* e, const char* histogram);
 
 #if defined(UNIT_TEST)
-  void TrackTerminatedExtensionForTest(const Extension* extension) {
+  void TrackTerminatedExtensionForTest(const extensions::Extension* extension) {
     TrackTerminatedExtension(extension);
   }
 #endif
@@ -636,7 +644,8 @@ class ExtensionService
   typedef std::list<NaClModuleInfo> NaClModuleInfoList;
 
   // Return true if the sync type of |extension| matches |type|.
-  bool IsCorrectSyncType(const Extension& extension, syncable::ModelType type)
+  bool IsCorrectSyncType(const extensions::Extension& extension,
+                         syncable::ModelType type)
       const;
 
   // Handles setting the extension specific values in |extension_sync_data| to
@@ -649,24 +658,25 @@ class ExtensionService
 
   // Look up an extension by ID, optionally including either or both of enabled
   // and disabled extensions.
-  const Extension* GetExtensionByIdInternal(const std::string& id,
-                                            bool include_enabled,
-                                            bool include_disabled,
-                                            bool include_terminated) const;
+  const extensions::Extension* GetExtensionByIdInternal(
+      const std::string& id,
+      bool include_enabled,
+      bool include_disabled,
+      bool include_terminated) const;
 
   // Adds the given extension to the list of terminated extensions if
   // it is not already there and unloads it.
-  void TrackTerminatedExtension(const Extension* extension);
+  void TrackTerminatedExtension(const extensions::Extension* extension);
 
   // Removes the extension with the given id from the list of
   // terminated extensions if it is there.
   void UntrackTerminatedExtension(const std::string& id);
 
   // Handles sending notification that |extension| was loaded.
-  void NotifyExtensionLoaded(const Extension* extension);
+  void NotifyExtensionLoaded(const extensions::Extension* extension);
 
   // Handles sending notification that |extension| was unloaded.
-  void NotifyExtensionUnloaded(const Extension* extension,
+  void NotifyExtensionUnloaded(const extensions::Extension* extension,
                                extension_misc::UnloadedExtensionReason reason);
 
   // Helper that updates the active extension list used for crash reporting.
@@ -716,7 +726,8 @@ class ExtensionService
 
   // Holds a map between renderer process IDs that are associated with an
   // installed app and their app.
-  typedef std::map<int, scoped_refptr<const Extension> > InstalledAppMap;
+  typedef std::map<int, scoped_refptr<const extensions::Extension> >
+      InstalledAppMap;
   InstalledAppMap installed_app_hosts_;
 
   // The full path to the directory where extensions are installed.
diff --git a/chrome/browser/extensions/extension_service_unittest.cc b/chrome/browser/extensions/extension_service_unittest.cc
index 3963400..127a2a1 100644
--- a/chrome/browser/extensions/extension_service_unittest.cc
+++ b/chrome/browser/extensions/extension_service_unittest.cc
@@ -95,6 +95,7 @@ using content::BrowserThread;
 using content::DOMStorageContext;
 using content::IndexedDBContext;
 using content::PluginService;
+using extensions::Extension;
 
 namespace keys = extension_manifest_keys;
 
@@ -523,9 +524,10 @@ class ExtensionServiceTest
 
       case chrome::NOTIFICATION_EXTENSION_UNLOADED: {
         const Extension* e =
-            content::Details<UnloadedExtensionInfo>(details)->extension;
+            content::Details<extensions::UnloadedExtensionInfo>(
+                details)->extension;
         unloaded_id_ = e->id();
-        ExtensionList::iterator i =
+        extensions::ExtensionList::iterator i =
             std::find(loaded_.begin(), loaded_.end(), e);
         // TODO(erikkay) fix so this can be an assert.  Right now the tests
         // are manually calling clear() on loaded_, so this isn't doable.
@@ -944,7 +946,7 @@ class ExtensionServiceTest
   }
 
  protected:
-  ExtensionList loaded_;
+  extensions::ExtensionList loaded_;
   std::string unloaded_id_;
   const Extension* installed_;
 
diff --git a/chrome/browser/extensions/extension_sorting.cc b/chrome/browser/extensions/extension_sorting.cc
index f7b770d..1e29b36 100644
--- a/chrome/browser/extensions/extension_sorting.cc
+++ b/chrome/browser/extensions/extension_sorting.cc
@@ -496,7 +496,7 @@ void ExtensionSorting::RemoveOrdinalMapping(
 
 void ExtensionSorting::SyncIfNeeded(const std::string& extension_id) {
   if (extension_service_) {
-    const Extension* ext =
+    const extensions::Extension* ext =
         extension_service_->GetInstalledExtension(extension_id);
 
     if (ext) {
diff --git a/chrome/browser/extensions/extension_sorting_unittest.cc b/chrome/browser/extensions/extension_sorting_unittest.cc
index ed16f68..1cd8316 100644
--- a/chrome/browser/extensions/extension_sorting_unittest.cc
+++ b/chrome/browser/extensions/extension_sorting_unittest.cc
@@ -7,6 +7,8 @@
 #include "chrome/common/extensions/extension_manifest_constants.h"
 #include "testing/gtest/include/gtest/gtest.h"
 
+using extensions::Extension;
+
 namespace keys = extension_manifest_keys;
 
 class ExtensionSortingTest : public ExtensionPrefsTest {
diff --git a/chrome/browser/extensions/extension_special_storage_policy.cc b/chrome/browser/extensions/extension_special_storage_policy.cc
index 23e6889..1b971bc 100644
--- a/chrome/browser/extensions/extension_special_storage_policy.cc
+++ b/chrome/browser/extensions/extension_special_storage_policy.cc
@@ -61,7 +61,7 @@ bool ExtensionSpecialStoragePolicy::IsFileHandler(
 }
 
 void ExtensionSpecialStoragePolicy::GrantRightsForExtension(
-    const Extension* extension) {
+    const extensions::Extension* extension) {
   DCHECK(extension);
   if (!extension->is_hosted_app() &&
       !extension->HasAPIPermission(
@@ -85,7 +85,7 @@ void ExtensionSpecialStoragePolicy::GrantRightsForExtension(
 }
 
 void ExtensionSpecialStoragePolicy::RevokeRightsForExtension(
-    const Extension* extension) {
+    const extensions::Extension* extension) {
   DCHECK(extension);
   if (!extension->is_hosted_app() &&
       !extension->HasAPIPermission(
@@ -158,13 +158,13 @@ bool ExtensionSpecialStoragePolicy::SpecialCollection::ContainsExtension(
 }
 
 void ExtensionSpecialStoragePolicy::SpecialCollection::Add(
-    const Extension* extension) {
+    const extensions::Extension* extension) {
   cached_results_.clear();
   extensions_[extension->id()] = extension;
 }
 
 void ExtensionSpecialStoragePolicy::SpecialCollection::Remove(
-    const Extension* extension) {
+    const extensions::Extension* extension) {
   cached_results_.clear();
   extensions_.erase(extension->id());
 }
diff --git a/chrome/browser/extensions/extension_special_storage_policy.h b/chrome/browser/extensions/extension_special_storage_policy.h
index 22a6c98..c2c8665 100644
--- a/chrome/browser/extensions/extension_special_storage_policy.h
+++ b/chrome/browser/extensions/extension_special_storage_policy.h
@@ -14,7 +14,10 @@
 #include "webkit/quota/special_storage_policy.h"
 
 class CookieSettings;
+
+namespace extensions {
 class Extension;
+}
 
 // Special rights are granted to 'extensions' and 'applications'. The
 // storage subsystems and the browsing data remover query this interface
@@ -32,8 +35,8 @@ class ExtensionSpecialStoragePolicy : public quota::SpecialStoragePolicy {
   virtual bool HasSessionOnlyOrigins() OVERRIDE;
 
   // Methods used by the ExtensionService to populate this class.
-  void GrantRightsForExtension(const Extension* extension);
-  void RevokeRightsForExtension(const Extension* extension);
+  void GrantRightsForExtension(const extensions::Extension* extension);
+  void RevokeRightsForExtension(const extensions::Extension* extension);
   void RevokeRightsForAllExtensions();
 
  protected:
@@ -47,13 +50,14 @@ class ExtensionSpecialStoragePolicy : public quota::SpecialStoragePolicy {
 
     bool Contains(const GURL& origin);
     bool ContainsExtension(const std::string& extension_id);
-    void Add(const Extension* extension);
-    void Remove(const Extension* extension);
+    void Add(const extensions::Extension* extension);
+    void Remove(const extensions::Extension* extension);
     void Clear();
 
    private:
     typedef std::map<GURL, bool> CachedResults;
-    typedef std::map<std::string, scoped_refptr<const Extension> > Extensions;
+    typedef std::map<std::string, scoped_refptr<const extensions::Extension> >
+        Extensions;
     Extensions extensions_;
     CachedResults cached_results_;
   };
diff --git a/chrome/browser/extensions/extension_special_storage_policy_unittest.cc b/chrome/browser/extensions/extension_special_storage_policy_unittest.cc
index 73dd57c..cb81acf 100644
--- a/chrome/browser/extensions/extension_special_storage_policy_unittest.cc
+++ b/chrome/browser/extensions/extension_special_storage_policy_unittest.cc
@@ -15,6 +15,7 @@
 #include "testing/gtest/include/gtest/gtest.h"
 
 using content::BrowserThread;
+using extensions::Extension;
 
 namespace keys = extension_manifest_keys;
 
diff --git a/chrome/browser/extensions/extension_startup_browsertest.cc b/chrome/browser/extensions/extension_startup_browsertest.cc
index d2a5f53..c35ff72 100644
--- a/chrome/browser/extensions/extension_startup_browsertest.cc
+++ b/chrome/browser/extensions/extension_startup_browsertest.cc
@@ -90,7 +90,7 @@ class ExtensionStartupTestBase : public InProcessBrowserTest {
     int found_extensions = 0;
     for (ExtensionSet::const_iterator it = service->extensions()->begin();
          it != service->extensions()->end(); ++it)
-      if ((*it)->location() != Extension::COMPONENT)
+      if ((*it)->location() != extensions::Extension::COMPONENT)
         found_extensions++;
 
     ASSERT_EQ(static_cast<uint32>(num_expected_extensions),
@@ -172,12 +172,12 @@ IN_PROC_BROWSER_TEST_F(ExtensionsStartupTest, MAYBE_NoFileAccess) {
 
   // Keep a separate list of extensions for which to disable file access, since
   // doing so reloads them.
-  std::vector<const Extension*> extension_list;
+  std::vector<const extensions::Extension*> extension_list;
 
   ExtensionService* service = browser()->profile()->GetExtensionService();
   for (ExtensionSet::const_iterator it = service->extensions()->begin();
        it != service->extensions()->end(); ++it) {
-    if ((*it)->location() == Extension::COMPONENT)
+    if ((*it)->location() == extensions::Extension::COMPONENT)
       continue;
     if (service->AllowFileAccess(*it))
       extension_list.push_back(*it);
diff --git a/chrome/browser/extensions/extension_sync_bundle.h b/chrome/browser/extensions/extension_sync_bundle.h
index 2945442..8d6379a 100644
--- a/chrome/browser/extensions/extension_sync_bundle.h
+++ b/chrome/browser/extensions/extension_sync_bundle.h
@@ -17,13 +17,14 @@
 #include "sync/api/syncable_service.h"
 
 class SyncChangeProcessor;
-class Extension;
 class ExtensionService;
 class ExtensionSet;
 class SyncErrorFactory;
 
 namespace extensions {
 
+class Extension;
+
 // Bundle of extension specific sync stuff.
 class ExtensionSyncBundle {
  public:
diff --git a/chrome/browser/extensions/extension_sync_data.h b/chrome/browser/extensions/extension_sync_data.h
index 9dd1514..ef3a92b 100644
--- a/chrome/browser/extensions/extension_sync_data.h
+++ b/chrome/browser/extensions/extension_sync_data.h
@@ -13,7 +13,6 @@
 #include "googleurl/src/gurl.h"
 #include "sync/api/sync_change.h"
 
-class Extension;
 class SyncData;
 
 namespace sync_pb {
@@ -22,6 +21,8 @@ class ExtensionSpecifics;
 
 namespace extensions {
 
+class Extension;
+
 // A class that encapsulates the synced properties of an Extension.
 class ExtensionSyncData {
  public:
diff --git a/chrome/browser/extensions/extension_system.cc b/chrome/browser/extensions/extension_system.cc
index 9385568..1cc0ccc 100644
--- a/chrome/browser/extensions/extension_system.cc
+++ b/chrome/browser/extensions/extension_system.cc
@@ -302,9 +302,9 @@ ExtensionSystemImpl::rules_registry_service() {
 }
 
 void ExtensionSystemImpl::RegisterExtensionWithRequestContexts(
-    const Extension* extension) {
+    const extensions::Extension* extension) {
   base::Time install_time;
-  if (extension->location() != Extension::COMPONENT) {
+  if (extension->location() != extensions::Extension::COMPONENT) {
     install_time = extension_service()->extension_prefs()->
         GetInstallTime(extension->id());
   }
diff --git a/chrome/browser/extensions/extension_system.h b/chrome/browser/extensions/extension_system.h
index 9b1d14ad..2ae71cc 100644
--- a/chrome/browser/extensions/extension_system.h
+++ b/chrome/browser/extensions/extension_system.h
@@ -13,7 +13,6 @@
 #include "chrome/browser/profiles/profile_keyed_service.h"
 #include "chrome/common/extensions/extension_constants.h"
 
-class Extension;
 class ExtensionDevToolsManager;
 class ExtensionEventRouter;
 class ExtensionInfoMap;
@@ -27,6 +26,7 @@ class UserScriptMaster;
 
 namespace extensions {
 class AlarmManager;
+class Extension;
 class LazyBackgroundTaskQueue;
 class RulesRegistryService;
 }
@@ -89,7 +89,7 @@ class ExtensionSystem : public ProfileKeyedService {
   // avoid race conditions by making sure URLRequestContexts learn about new
   // extensions before anything else needs them to know.
   virtual void RegisterExtensionWithRequestContexts(
-      const Extension* extension) {}
+      const extensions::Extension* extension) {}
 
   // Called by the ExtensionService that lives in this system. Lets the
   // info map clean up its RequestContexts once all the listeners to the
@@ -129,7 +129,7 @@ class ExtensionSystemImpl : public ExtensionSystem {
       OVERRIDE;  // shared
 
   virtual void RegisterExtensionWithRequestContexts(
-      const Extension* extension) OVERRIDE;
+      const extensions::Extension* extension) OVERRIDE;
 
   virtual void UnregisterExtensionWithRequestContexts(
       const std::string& extension_id,
diff --git a/chrome/browser/extensions/extension_tab_helper.cc b/chrome/browser/extensions/extension_tab_helper.cc
index 8f1a554..c7c1c5c 100644
--- a/chrome/browser/extensions/extension_tab_helper.cc
+++ b/chrome/browser/extensions/extension_tab_helper.cc
@@ -31,6 +31,7 @@
 #include "ui/gfx/image/image.h"
 
 using content::WebContents;
+using extensions::Extension;
 using extensions::ScriptBadgeController;
 using extensions::ScriptExecutorImpl;
 using extensions::PageActionController;
diff --git a/chrome/browser/extensions/extension_tab_helper.h b/chrome/browser/extensions/extension_tab_helper.h
index fcda259..d4a4402 100644
--- a/chrome/browser/extensions/extension_tab_helper.h
+++ b/chrome/browser/extensions/extension_tab_helper.h
@@ -16,7 +16,6 @@
 #include "content/public/browser/web_contents_observer.h"
 #include "third_party/skia/include/core/SkBitmap.h"
 
-class Extension;
 class ExtensionTabHelperDelegate;
 class TabContentsWrapper;
 struct WebApplicationInfo;
@@ -27,6 +26,7 @@ struct LoadCommittedDetails;
 
 namespace extensions {
 class ActionBoxController;
+class Extension;
 class ScriptBadgeController;
 class ScriptExecutor;
 }
@@ -79,7 +79,7 @@ class ExtensionTabHelper
   // NOTE: this should only be manipulated before the tab is added to a browser.
   // TODO(sky): resolve if this is the right way to identify an app tab. If it
   // is, than this should be passed in the constructor.
-  void SetExtensionApp(const Extension* extension);
+  void SetExtensionApp(const extensions::Extension* extension);
 
   // Convenience for setting the app extension by id. This does nothing if
   // |extension_app_id| is empty, or an extension can't be found given the
@@ -89,7 +89,7 @@ class ExtensionTabHelper
   // Set just the app icon, used by panels created by an extension.
   void SetExtensionAppIconById(const std::string& extension_app_id);
 
-  const Extension* extension_app() const { return extension_app_; }
+  const extensions::Extension* extension_app() const { return extension_app_; }
   bool is_app() const { return extension_app_ != NULL; }
   const WebApplicationInfo& web_app_info() const {
     return web_app_info_;
@@ -150,9 +150,10 @@ class ExtensionTabHelper
 
   // Resets app_icon_ and if |extension| is non-null creates a new
   // ImageLoadingTracker to load the extension's image.
-  void UpdateExtensionAppIcon(const Extension* extension);
+  void UpdateExtensionAppIcon(const extensions::Extension* extension);
 
-  const Extension* GetExtension(const std::string& extension_app_id);
+  const extensions::Extension* GetExtension(
+      const std::string& extension_app_id);
 
   // ImageLoadingTracker::Observer.
   virtual void OnImageLoaded(const gfx::Image& image,
@@ -183,7 +184,7 @@ class ExtensionTabHelper
 
   // If non-null this tab is an app tab and this is the extension the tab was
   // created for.
-  const Extension* extension_app_;
+  const extensions::Extension* extension_app_;
 
   // Icon for extension_app_ (if non-null) or a manually-set icon for
   // non-extension apps.
diff --git a/chrome/browser/extensions/extension_tab_util.cc b/chrome/browser/extensions/extension_tab_util.cc
index ba6a778..2e2db28 100644
--- a/chrome/browser/extensions/extension_tab_util.cc
+++ b/chrome/browser/extensions/extension_tab_util.cc
@@ -207,7 +207,7 @@ bool ExtensionTabUtil::GetTabById(int tab_id,
 }
 
 GURL ExtensionTabUtil::ResolvePossiblyRelativeURL(const std::string& url_string,
-                                                  const Extension* extension) {
+    const extensions::Extension* extension) {
   GURL url = GURL(url_string);
   if (!url.is_valid())
     url = extension->GetResourceURL(url_string);
diff --git a/chrome/browser/extensions/extension_tab_util.h b/chrome/browser/extensions/extension_tab_util.h
index ed0f1a5..d6659e6 100644
--- a/chrome/browser/extensions/extension_tab_util.h
+++ b/chrome/browser/extensions/extension_tab_util.h
@@ -9,7 +9,6 @@
 #include <string>
 
 class Browser;
-class Extension;
 class GURL;
 class Profile;
 class TabContentsWrapper;
@@ -24,6 +23,10 @@ namespace content {
 class WebContents;
 }
 
+namespace extensions {
+class Extension;
+}
+
 // Provides various utility functions that help manipulate tabs.
 class ExtensionTabUtil {
  public:
@@ -71,7 +74,7 @@ class ExtensionTabUtil {
   // extension base, we decided it wasn't worth breaking existing extensions to
   // fix.
   static GURL ResolvePossiblyRelativeURL(const std::string& url_string,
-                                         const Extension* extension);
+      const extensions::Extension* extension);
 
   // Returns true if |url| is used for testing crashes.
   static bool IsCrashURL(const GURL& url);
diff --git a/chrome/browser/extensions/extension_tabs_module.h b/chrome/browser/extensions/extension_tabs_module.h
index 7d9d81d..58ee8ed 100644
--- a/chrome/browser/extensions/extension_tabs_module.h
+++ b/chrome/browser/extensions/extension_tabs_module.h
@@ -16,19 +16,21 @@
 #include "googleurl/src/gurl.h"
 
 class BackingStore;
-class Extension;
 class GURL;
 class SkBitmap;
 class TabContentsWrapper;
+
 namespace base {
 class DictionaryValue;
-}  // namespace base
+}
+
 namespace content {
 class WebContents;
-}  // namespace content
+}
+
 namespace skia {
 class PlatformCanvas;
-}  // namespace skia
+}
 
 // Windows
 class GetWindowFunction : public SyncExtensionFunction {
diff --git a/chrome/browser/extensions/extension_tabs_test.cc b/chrome/browser/extensions/extension_tabs_test.cc
index 58e2bb7..393a9c0 100644
--- a/chrome/browser/extensions/extension_tabs_test.cc
+++ b/chrome/browser/extensions/extension_tabs_test.cc
@@ -247,7 +247,8 @@ IN_PROC_BROWSER_TEST_F(ExtensionTabsTest, UpdateNoPermissions) {
   // The test empty extension has no permissions, therefore it should not get
   // tab data in the function result.
   scoped_refptr<UpdateTabFunction> update_tab_function(new UpdateTabFunction());
-  scoped_refptr<Extension> empty_extension(utils::CreateEmptyExtension());
+  scoped_refptr<extensions::Extension> empty_extension(
+      utils::CreateEmptyExtension());
   update_tab_function->set_extension(empty_extension.get());
   // Without a callback the function will not generate a result.
   update_tab_function->set_has_callback(true);
diff --git a/chrome/browser/extensions/extension_toolbar_model.cc b/chrome/browser/extensions/extension_toolbar_model.cc
index 5c063a8..d1ea347 100644
--- a/chrome/browser/extensions/extension_toolbar_model.cc
+++ b/chrome/browser/extensions/extension_toolbar_model.cc
@@ -15,6 +15,9 @@
 #include "content/public/browser/notification_details.h"
 #include "content/public/browser/notification_source.h"
 
+using extensions::Extension;
+using extensions::ExtensionList;
+
 ExtensionToolbarModel::ExtensionToolbarModel(ExtensionService* service)
     : service_(service),
       prefs_(service->profile()->GetPrefs()),
@@ -101,7 +104,8 @@ void ExtensionToolbarModel::Observe(
 
   const Extension* extension = NULL;
   if (type == chrome::NOTIFICATION_EXTENSION_UNLOADED) {
-    extension = content::Details<UnloadedExtensionInfo>(details)->extension;
+    extension = content::Details<extensions::UnloadedExtensionInfo>(
+        details)->extension;
   } else {
     extension = content::Details<const Extension>(details).ptr();
   }
diff --git a/chrome/browser/extensions/extension_toolbar_model.h b/chrome/browser/extensions/extension_toolbar_model.h
index 8dca018..530340a 100644
--- a/chrome/browser/extensions/extension_toolbar_model.h
+++ b/chrome/browser/extensions/extension_toolbar_model.h
@@ -28,13 +28,15 @@ class ExtensionToolbarModel : public content::NotificationObserver {
    public:
     // An extension with a browser action button has been added, and should go
     // in the toolbar at |index|.
-    virtual void BrowserActionAdded(const Extension* extension, int index) {}
+    virtual void BrowserActionAdded(const extensions::Extension* extension,
+                                    int index) {}
 
     // The browser action button for |extension| should no longer show.
-    virtual void BrowserActionRemoved(const Extension* extension) {}
+    virtual void BrowserActionRemoved(const extensions::Extension* extension) {}
 
     // The browser action button for |extension| has been moved to |index|.
-    virtual void BrowserActionMoved(const Extension* extension, int index) {}
+    virtual void BrowserActionMoved(const extensions::Extension* extension,
+                                    int index) {}
 
     // The browser action button for |extension_id| (which was not a popup) was
     // clicked, executing it.
@@ -51,7 +53,7 @@ class ExtensionToolbarModel : public content::NotificationObserver {
   // Functions called by the view.
   void AddObserver(Observer* observer);
   void RemoveObserver(Observer* observer);
-  void MoveBrowserAction(const Extension* extension, int index);
+  void MoveBrowserAction(const extensions::Extension* extension, int index);
   void ExecuteBrowserAction(const std::string& extension_id, Browser* browser);
   // If count == size(), this will set the visible icon count to -1, meaning
   // "show all actions".
@@ -65,15 +67,15 @@ class ExtensionToolbarModel : public content::NotificationObserver {
     return toolitems_.size();
   }
 
-  ExtensionList::iterator begin() {
+  extensions::ExtensionList::iterator begin() {
     return toolitems_.begin();
   }
 
-  ExtensionList::iterator end() {
+  extensions::ExtensionList::iterator end() {
     return toolitems_.end();
   }
 
-  const Extension* GetExtensionByIndex(int index) const;
+  const extensions::Extension* GetExtensionByIndex(int index) const;
 
   // Utility functions for converting between an index into the list of
   // incognito-enabled browser actions, and the list of all browser actions.
@@ -97,8 +99,8 @@ class ExtensionToolbarModel : public content::NotificationObserver {
   // Our observers.
   ObserverList<Observer> observers_;
 
-  void AddExtension(const Extension* extension);
-  void RemoveExtension(const Extension* extension);
+  void AddExtension(const extensions::Extension* extension);
+  void RemoveExtension(const extensions::Extension* extension);
 
   // Our ExtensionService, guaranteed to outlive us.
   ExtensionService* service_;
@@ -109,7 +111,7 @@ class ExtensionToolbarModel : public content::NotificationObserver {
   bool extensions_initialized_;
 
   // Ordered list of browser action buttons.
-  ExtensionList toolitems_;
+  extensions::ExtensionList toolitems_;
 
   // Keeps track of what the last extension to get disabled was.
   std::string last_extension_removed_;
diff --git a/chrome/browser/extensions/extension_toolbar_model_browsertest.cc b/chrome/browser/extensions/extension_toolbar_model_browsertest.cc
index bf74f3c..8221c66 100644
--- a/chrome/browser/extensions/extension_toolbar_model_browsertest.cc
+++ b/chrome/browser/extensions/extension_toolbar_model_browsertest.cc
@@ -10,6 +10,8 @@
 #include "chrome/common/chrome_switches.h"
 #include "chrome/test/base/in_process_browser_test.h"
 
+using extensions::Extension;
+
 // An InProcessBrowserTest for testing the ExtensionToolbarModel.
 // TODO(erikkay) It's unfortunate that this needs to be an in-proc browser test.
 // It would be nice to refactor things so that ExtensionService could run
@@ -48,7 +50,8 @@ class ExtensionToolbarModelTest : public ExtensionBrowserTest,
   }
 
   const Extension* ExtensionAt(int index) {
-    for (ExtensionList::iterator i = model_->begin(); i < model_->end(); ++i) {
+    for (extensions::ExtensionList::iterator i = model_->begin();
+         i < model_->end(); ++i) {
       if (index-- == 0)
         return *i;
     }
diff --git a/chrome/browser/extensions/extension_ui_unittest.cc b/chrome/browser/extensions/extension_ui_unittest.cc
index 190fe68..e55c0ad 100644
--- a/chrome/browser/extensions/extension_ui_unittest.cc
+++ b/chrome/browser/extensions/extension_ui_unittest.cc
@@ -10,6 +10,7 @@
 #include "chrome/common/extensions/extension.h"
 #include "testing/gtest/include/gtest/gtest.h"
 
+using extensions::Extension;
 
 class ExtensionUITest : public testing::Test {
  protected:
diff --git a/chrome/browser/extensions/extension_uninstall_dialog.cc b/chrome/browser/extensions/extension_uninstall_dialog.cc
index 554e929..13c718e 100644
--- a/chrome/browser/extensions/extension_uninstall_dialog.cc
+++ b/chrome/browser/extensions/extension_uninstall_dialog.cc
@@ -29,7 +29,8 @@ ExtensionUninstallDialog::ExtensionUninstallDialog(
 
 ExtensionUninstallDialog::~ExtensionUninstallDialog() {}
 
-void ExtensionUninstallDialog::ConfirmUninstall(const Extension* extension) {
+void ExtensionUninstallDialog::ConfirmUninstall(
+    const extensions::Extension* extension) {
   DCHECK(ui_loop_ == MessageLoop::current());
   extension_ = extension;
 
diff --git a/chrome/browser/extensions/extension_uninstall_dialog.h b/chrome/browser/extensions/extension_uninstall_dialog.h
index b03561d..83b4ab1 100644
--- a/chrome/browser/extensions/extension_uninstall_dialog.h
+++ b/chrome/browser/extensions/extension_uninstall_dialog.h
@@ -15,6 +15,10 @@
 class MessageLoop;
 class Profile;
 
+namespace extensions {
+class Extension;
+}
+
 class ExtensionUninstallDialog
     : public ImageLoadingTracker::Observer,
       public base::SupportsWeakPtr<ExtensionUninstallDialog> {
@@ -41,7 +45,7 @@ class ExtensionUninstallDialog
   // Starts the process of showing a confirmation UI, which is split into two.
   // 1) Set off a 'load icon' task.
   // 2) Handle the load icon response and show the UI (OnImageLoaded).
-  void ConfirmUninstall(const Extension* extension);
+  void ConfirmUninstall(const extensions::Extension* extension);
 
  protected:
   // Constructor used by the derived classes.
@@ -53,7 +57,7 @@ class ExtensionUninstallDialog
   Delegate* delegate_;
 
   // The extension we are showing the dialog for.
-  const Extension* extension_;
+  const extensions::Extension* extension_;
 
   // The extensions icon.
   SkBitmap icon_;
diff --git a/chrome/browser/extensions/extension_web_ui.cc b/chrome/browser/extensions/extension_web_ui.cc
index 809e9df..429f5bb 100644
--- a/chrome/browser/extensions/extension_web_ui.cc
+++ b/chrome/browser/extensions/extension_web_ui.cc
@@ -35,6 +35,7 @@
 #include "ui/gfx/favicon_size.h"
 
 using content::WebContents;
+using extensions::Extension;
 
 namespace {
 
diff --git a/chrome/browser/extensions/extension_web_ui.h b/chrome/browser/extensions/extension_web_ui.h
index 60eb446..e67e748 100644
--- a/chrome/browser/extensions/extension_web_ui.h
+++ b/chrome/browser/extensions/extension_web_ui.h
@@ -42,9 +42,9 @@ class ExtensionWebUI : public content::WebUIController {
   // Page names are the keys, and chrome-extension: URLs are the values.
   // (e.g. { "newtab": "chrome-extension://<id>/my_new_tab.html" }
   static void RegisterChromeURLOverrides(Profile* profile,
-      const Extension::URLOverrideMap& overrides);
+      const extensions::Extension::URLOverrideMap& overrides);
   static void UnregisterChromeURLOverrides(Profile* profile,
-      const Extension::URLOverrideMap& overrides);
+      const extensions::Extension::URLOverrideMap& overrides);
   static void UnregisterChromeURLOverride(const std::string& page,
                                           Profile* profile,
                                           base::Value* override);
diff --git a/chrome/browser/extensions/extension_webkit_preferences.cc b/chrome/browser/extensions/extension_webkit_preferences.cc
index 0cf402c..672ba58 100644
--- a/chrome/browser/extensions/extension_webkit_preferences.cc
+++ b/chrome/browser/extensions/extension_webkit_preferences.cc
@@ -11,7 +11,7 @@
 
 namespace extension_webkit_preferences {
 
-void SetPreferences(const Extension* extension,
+void SetPreferences(const extensions::Extension* extension,
                     content::ViewType render_view_type,
                     webkit_glue::WebPreferences* webkit_prefs) {
   if (!extension)
@@ -51,7 +51,7 @@ void SetPreferences(const Extension* extension,
   // sometimes loaded with chrome-extension: URLs - we should expect the
   // performance characteristics to be similar in both cases.
   const CommandLine& command_line = *CommandLine::ForCurrentProcess();
-  if (extension->location() == Extension::COMPONENT &&
+  if (extension->location() == extensions::Extension::COMPONENT &&
       !command_line.HasSwitch(switches::kAllowWebUICompositing)) {
     webkit_prefs->accelerated_compositing_enabled = false;
     webkit_prefs->accelerated_2d_canvas_enabled = false;
diff --git a/chrome/browser/extensions/extension_webkit_preferences.h b/chrome/browser/extensions/extension_webkit_preferences.h
index f5c1fb4..e793bb0 100644
--- a/chrome/browser/extensions/extension_webkit_preferences.h
+++ b/chrome/browser/extensions/extension_webkit_preferences.h
@@ -7,7 +7,9 @@
 
 #include "chrome/common/chrome_view_type.h"
 
+namespace extensions {
 class Extension;
+}
 
 namespace webkit_glue {
 struct WebPreferences;
@@ -15,7 +17,7 @@ struct WebPreferences;
 
 namespace extension_webkit_preferences {
 
-void SetPreferences(const Extension* extension,
+void SetPreferences(const extensions::Extension* extension,
                     content::ViewType render_view_type,
                     webkit_glue::WebPreferences* webkit_prefs);
 
diff --git a/chrome/browser/extensions/extension_webstore_private_api.cc b/chrome/browser/extensions/extension_webstore_private_api.cc
index f2d1135..8aa813b 100644
--- a/chrome/browser/extensions/extension_webstore_private_api.cc
+++ b/chrome/browser/extensions/extension_webstore_private_api.cc
@@ -259,7 +259,7 @@ bool BeginInstallWithManifestFunction::RunImpl() {
   CHECK(details);
 
   EXTENSION_FUNCTION_VALIDATE(details->GetString(kIdKey, &id_));
-  if (!Extension::IdIsValid(id_)) {
+  if (!extensions::Extension::IdIsValid(id_)) {
     SetResult(INVALID_ID);
     error_ = kInvalidIdError;
     return false;
@@ -448,7 +448,7 @@ void BeginInstallWithManifestFunction::InstallUIAbort(bool user_initiated) {
 bool CompleteInstallFunction::RunImpl() {
   std::string id;
   EXTENSION_FUNCTION_VALIDATE(args_->GetString(0, &id));
-  if (!Extension::IdIsValid(id)) {
+  if (!extensions::Extension::IdIsValid(id)) {
     error_ = kInvalidIdError;
     return false;
   }
diff --git a/chrome/browser/extensions/extension_webstore_private_api.h b/chrome/browser/extensions/extension_webstore_private_api.h
index 912f9d7..4c31ab4 100644
--- a/chrome/browser/extensions/extension_webstore_private_api.h
+++ b/chrome/browser/extensions/extension_webstore_private_api.h
@@ -145,7 +145,7 @@ class BeginInstallWithManifestFunction
 
   // A dummy Extension object we create for the purposes of using
   // ExtensionInstallUI to prompt for confirmation of the install.
-  scoped_refptr<Extension> dummy_extension_;
+  scoped_refptr<extensions::Extension> dummy_extension_;
 
   // The class that displays the install prompt.
   scoped_ptr<ExtensionInstallUI> install_ui_;
diff --git a/chrome/browser/extensions/external_extension_provider_impl.cc b/chrome/browser/extensions/external_extension_provider_impl.cc
index 46c3385..ea245c3 100644
--- a/chrome/browser/extensions/external_extension_provider_impl.cc
+++ b/chrome/browser/extensions/external_extension_provider_impl.cc
@@ -40,6 +40,7 @@
 #endif
 
 using content::BrowserThread;
+using extensions::Extension;
 
 // Constants for keeping track of extension preferences in a dictionary.
 const char ExternalExtensionProviderImpl::kExternalCrx[] = "external_crx";
diff --git a/chrome/browser/extensions/external_extension_provider_impl.h b/chrome/browser/extensions/external_extension_provider_impl.h
index 1436fdf..9de9374 100644
--- a/chrome/browser/extensions/external_extension_provider_impl.h
+++ b/chrome/browser/extensions/external_extension_provider_impl.h
@@ -21,6 +21,10 @@ namespace base {
 class DictionaryValue;
 }
 
+namespace extensions {
+class Extension;
+}
+
 // A specialization of the ExternalExtensionProvider that uses an instance
 // of ExternalExtensionLoader to provide external extensions. This class
 // can be seen as a bridge between the extension system and an
@@ -38,8 +42,8 @@ class ExternalExtensionProviderImpl
   ExternalExtensionProviderImpl(
       VisitorInterface* service,
       ExternalExtensionLoader* loader,
-      Extension::Location crx_location,
-      Extension::Location download_location,
+      extensions::Extension::Location crx_location,
+      extensions::Extension::Location download_location,
       int creation_flags);
 
   virtual ~ExternalExtensionProviderImpl();
@@ -59,7 +63,7 @@ class ExternalExtensionProviderImpl
   virtual void VisitRegisteredExtension() OVERRIDE;
   virtual bool HasExtension(const std::string& id) const OVERRIDE;
   virtual bool GetExtensionDetails(const std::string& id,
-                                   Extension::Location* location,
+                                   extensions::Extension::Location* location,
                                    scoped_ptr<Version>* version) const OVERRIDE;
 
   virtual bool IsReady() const OVERRIDE;
@@ -77,11 +81,11 @@ class ExternalExtensionProviderImpl
  private:
   // Location for external extensions that are provided by this provider from
   // local crx files.
-  const Extension::Location crx_location_;
+  const extensions::Extension::Location crx_location_;
 
   // Location for external extensions that are provided by this provider from
   // update URLs.
-  const Extension::Location download_location_;
+  const extensions::Extension::Location download_location_;
 
   // Weak pointer to the object that consumes the external extensions.
   // This is zeroed out by: ServiceShutdown()
diff --git a/chrome/browser/extensions/external_extension_provider_interface.h b/chrome/browser/extensions/external_extension_provider_interface.h
index 03951ec..e765e42 100644
--- a/chrome/browser/extensions/external_extension_provider_interface.h
+++ b/chrome/browser/extensions/external_extension_provider_interface.h
@@ -32,7 +32,7 @@ class ExternalExtensionProviderInterface {
         const std::string& id,
         const Version* version,
         const FilePath& path,
-        Extension::Location location,
+        extensions::Extension::Location location,
         int creation_flags,
         bool mark_acknowledged) = 0;
 
@@ -42,7 +42,7 @@ class ExternalExtensionProviderInterface {
     virtual bool OnExternalExtensionUpdateUrlFound(
         const std::string& id,
         const GURL& update_url,
-        Extension::Location location) = 0;
+        extensions::Extension::Location location) = 0;
 
     // Called after all the external extensions have been reported
     // through the above two methods. |provider| is a pointer to the
@@ -74,7 +74,7 @@ class ExternalExtensionProviderInterface {
   // provider type, it will not be changed.
   // This function is no longer used outside unit tests.
   virtual bool GetExtensionDetails(const std::string& id,
-                                   Extension::Location* location,
+                                   extensions::Extension::Location* location,
                                    scoped_ptr<Version>* version) const = 0;
 
   // Determines if this provider had loaded the list of external extensions
diff --git a/chrome/browser/extensions/external_policy_extension_loader.cc b/chrome/browser/extensions/external_policy_extension_loader.cc
index fedeada..c0a9bf9 100644
--- a/chrome/browser/extensions/external_policy_extension_loader.cc
+++ b/chrome/browser/extensions/external_policy_extension_loader.cc
@@ -26,7 +26,7 @@ bool CheckExtension(const std::string& id, const std::string& update_url) {
                  << "extension: " << update_url;
     return false;
   }
-  if (!Extension::IdIsValid(id)) {
+  if (!extensions::Extension::IdIsValid(id)) {
     LOG(WARNING) << "Policy specifies invalid ID for external "
                  << "extension: " << id;
     return false;
diff --git a/chrome/browser/extensions/external_policy_extension_loader_unittest.cc b/chrome/browser/extensions/external_policy_extension_loader_unittest.cc
index cd5c3c4..69b5e0c 100644
--- a/chrome/browser/extensions/external_policy_extension_loader_unittest.cc
+++ b/chrome/browser/extensions/external_policy_extension_loader_unittest.cc
@@ -19,6 +19,7 @@
 #include "testing/gtest/include/gtest/gtest.h"
 
 using content::BrowserThread;
+using extensions::Extension;
 
 class ExternalPolicyExtensionProviderTest : public testing::Test {
  public:
diff --git a/chrome/browser/extensions/external_registry_extension_loader_win.cc b/chrome/browser/extensions/external_registry_extension_loader_win.cc
index a494be5..289617c 100644
--- a/chrome/browser/extensions/external_registry_extension_loader_win.cc
+++ b/chrome/browser/extensions/external_registry_extension_loader_win.cc
@@ -120,7 +120,7 @@ void ExternalRegistryExtensionLoader::LoadOnFileThread() {
 
     std::string id = WideToASCII(*it);
     StringToLowerASCII(&id);
-    if (!Extension::IdIsValid(id)) {
+    if (!extensions::Extension::IdIsValid(id)) {
       LOG(ERROR) << "Invalid id value " << id
                  << " for key " << key_path << ".";
       continue;
diff --git a/chrome/browser/extensions/image_loading_tracker.cc b/chrome/browser/extensions/image_loading_tracker.cc
index ab43b06..65d47ad 100644
--- a/chrome/browser/extensions/image_loading_tracker.cc
+++ b/chrome/browser/extensions/image_loading_tracker.cc
@@ -22,6 +22,7 @@
 #include "webkit/glue/image_decoder.h"
 
 using content::BrowserThread;
+using extensions::Extension;
 
 ////////////////////////////////////////////////////////////////////////////////
 // ImageLoadingTracker::Observer
@@ -327,7 +328,7 @@ void ImageLoadingTracker::Observe(int type,
   DCHECK(type == chrome::NOTIFICATION_EXTENSION_UNLOADED);
 
   const Extension* extension =
-      content::Details<UnloadedExtensionInfo>(details)->extension;
+      content::Details<extensions::UnloadedExtensionInfo>(details)->extension;
 
   // Remove reference to this extension from all pending load entries. This
   // ensures we don't attempt to cache the image when the load completes.
diff --git a/chrome/browser/extensions/image_loading_tracker.h b/chrome/browser/extensions/image_loading_tracker.h
index be89d34..8c92bf6 100644
--- a/chrome/browser/extensions/image_loading_tracker.h
+++ b/chrome/browser/extensions/image_loading_tracker.h
@@ -16,9 +16,12 @@
 #include "content/public/browser/notification_registrar.h"
 #include "ui/gfx/size.h"
 
-class Extension;
 class SkBitmap;
 
+namespace extensions {
+class Extension;
+}
+
 namespace gfx {
 class Image;
 }
@@ -77,7 +80,7 @@ class ImageLoadingTracker : public content::NotificationObserver {
   // |max_size| it will be resized to those dimensions. IMPORTANT NOTE: this
   // function may call back your observer synchronously (ie before it returns)
   // if the image was found in the cache.
-  void LoadImage(const Extension* extension,
+  void LoadImage(const extensions::Extension* extension,
                  const ExtensionResource& resource,
                  const gfx::Size& max_size,
                  CacheParam cache);
@@ -85,7 +88,7 @@ class ImageLoadingTracker : public content::NotificationObserver {
   // Same as LoadImage() above except it loads multiple images from the same
   // extension. This is used to load multiple resolutions of the same image
   // type.
-  void LoadImages(const Extension* extension,
+  void LoadImages(const extensions::Extension* extension,
                   const std::vector<ImageInfo>& info_list,
                   CacheParam cache);
 
@@ -100,7 +103,7 @@ class ImageLoadingTracker : public content::NotificationObserver {
     PendingLoadInfo();
     ~PendingLoadInfo();
 
-    const Extension* extension;
+    const extensions::Extension* extension;
     // This is cached separate from |extension| in case the extension in
     // unloaded.
     std::string extension_id;
@@ -126,7 +129,7 @@ class ImageLoadingTracker : public content::NotificationObserver {
   // Checks whether image is a component extension resource. Returns false
   // if a given |resource| does not have a corresponding image in bundled
   // resources. Otherwise fills |resource_id|.
-  bool IsComponentExtensionResource(const Extension* extension,
+  bool IsComponentExtensionResource(const extensions::Extension* extension,
                                     const ExtensionResource& resource,
                                     int& resource_id) const;
 
diff --git a/chrome/browser/extensions/image_loading_tracker_unittest.cc b/chrome/browser/extensions/image_loading_tracker_unittest.cc
index edbbcee..9fd69f3 100644
--- a/chrome/browser/extensions/image_loading_tracker_unittest.cc
+++ b/chrome/browser/extensions/image_loading_tracker_unittest.cc
@@ -21,6 +21,7 @@
 #include "ui/gfx/size.h"
 
 using content::BrowserThread;
+using extensions::Extension;
 
 class ImageLoadingTrackerTest : public testing::Test,
                                 public ImageLoadingTracker::Observer {
@@ -168,12 +169,12 @@ TEST_F(ImageLoadingTrackerTest, DeleteExtensionWhileWaitingForCache) {
   EXPECT_EQ(0, image_loaded_count());
 
   // Send out notification the extension was uninstalled.
-  UnloadedExtensionInfo details(extension.get(),
-                                extension_misc::UNLOAD_REASON_UNINSTALL);
+  extensions::UnloadedExtensionInfo details(extension.get(),
+      extension_misc::UNLOAD_REASON_UNINSTALL);
   content::NotificationService::current()->Notify(
       chrome::NOTIFICATION_EXTENSION_UNLOADED,
       content::NotificationService::AllSources(),
-      content::Details<UnloadedExtensionInfo>(&details));
+      content::Details<extensions::UnloadedExtensionInfo>(&details));
 
   // Chuck the extension, that way if anyone tries to access it we should crash
   // or get valgrind errors.
diff --git a/chrome/browser/extensions/installed_loader.cc b/chrome/browser/extensions/installed_loader.cc
index 4cd5af2..26fe121 100644
--- a/chrome/browser/extensions/installed_loader.cc
+++ b/chrome/browser/extensions/installed_loader.cc
@@ -23,6 +23,8 @@
 
 using content::BrowserThread;
 using content::UserMetricsAction;
+using extensions::Extension;
+using extensions::ExtensionInfo;
 
 namespace errors = extension_manifest_errors;
 
diff --git a/chrome/browser/extensions/installed_loader.h b/chrome/browser/extensions/installed_loader.h
index 774f10c..bd4ef079 100644
--- a/chrome/browser/extensions/installed_loader.h
+++ b/chrome/browser/extensions/installed_loader.h
@@ -6,13 +6,13 @@
 #define CHROME_BROWSER_EXTENSIONS_INSTALLED_LOADER_H_
 #pragma once
 
-class Extension;
 class ExtensionPrefs;
 class ExtensionService;
-struct ExtensionInfo;
 
 namespace extensions {
 
+struct ExtensionInfo;
+
 // Loads installed extensions from the prefs.
 class InstalledLoader {
  public:
diff --git a/chrome/browser/extensions/isolated_app_browsertest.cc b/chrome/browser/extensions/isolated_app_browsertest.cc
index 94e993b..6664eac 100644
--- a/chrome/browser/extensions/isolated_app_browsertest.cc
+++ b/chrome/browser/extensions/isolated_app_browsertest.cc
@@ -35,8 +35,8 @@ class IsolatedAppTest : public ExtensionBrowserTest {
     return actual_cookie.find(cookie) != std::string::npos;
   }
 
-  const Extension* GetInstalledApp(WebContents* contents) {
-    const Extension* installed_app = NULL;
+  const extensions::Extension* GetInstalledApp(WebContents* contents) {
+    const extensions::Extension* installed_app = NULL;
     Profile* profile =
         Profile::FromBrowserContext(contents->GetBrowserContext());
     ExtensionService* service = profile->GetExtensionService();
diff --git a/chrome/browser/extensions/lazy_background_page_apitest.cc b/chrome/browser/extensions/lazy_background_page_apitest.cc
index d5ddf9d..d257fcc 100644
--- a/chrome/browser/extensions/lazy_background_page_apitest.cc
+++ b/chrome/browser/extensions/lazy_background_page_apitest.cc
@@ -26,6 +26,8 @@
 #include "googleurl/src/gurl.h"
 #include "net/base/mock_host_resolver.h"
 
+using extensions::Extension;
+
 namespace {
 // Helper class to wait for a lazy background page to load and close again.
 class LazyBackgroundObserver {
diff --git a/chrome/browser/extensions/lazy_background_task_queue.h b/chrome/browser/extensions/lazy_background_task_queue.h
index abe71b2..d38c152 100644
--- a/chrome/browser/extensions/lazy_background_task_queue.h
+++ b/chrome/browser/extensions/lazy_background_task_queue.h
@@ -17,12 +17,13 @@
 #include "content/public/browser/notification_observer.h"
 #include "content/public/browser/notification_registrar.h"
 
-class Extension;
 class ExtensionHost;
 class Profile;
 
 namespace extensions {
 
+class Extension;
+
 // This class maintains a queue of tasks that should execute when an
 // extension's lazy background page is loaded. It is also in charge of loading
 // the page when the first task is queued.
diff --git a/chrome/browser/extensions/pending_extension_info.cc b/chrome/browser/extensions/pending_extension_info.cc
index d874626..38089d9 100644
--- a/chrome/browser/extensions/pending_extension_info.cc
+++ b/chrome/browser/extensions/pending_extension_info.cc
@@ -10,7 +10,7 @@ PendingExtensionInfo::PendingExtensionInfo(
     ShouldAllowInstallPredicate should_allow_install,
     bool is_from_sync,
     bool install_silently,
-    Extension::Location install_source)
+    extensions::Extension::Location install_source)
     : update_url_(update_url),
       version_(version),
       should_allow_install_(should_allow_install),
@@ -23,4 +23,4 @@ PendingExtensionInfo::PendingExtensionInfo()
       should_allow_install_(NULL),
       is_from_sync_(true),
       install_silently_(false),
-      install_source_(Extension::INVALID) {}
+      install_source_(extensions::Extension::INVALID) {}
diff --git a/chrome/browser/extensions/pending_extension_info.h b/chrome/browser/extensions/pending_extension_info.h
index fc7fd04..7af7074 100644
--- a/chrome/browser/extensions/pending_extension_info.h
+++ b/chrome/browser/extensions/pending_extension_info.h
@@ -18,7 +18,7 @@
 // PendingExtensionManager, and remove all other users.
 class PendingExtensionInfo {
  public:
-  typedef bool (*ShouldAllowInstallPredicate)(const Extension&);
+  typedef bool (*ShouldAllowInstallPredicate)(const extensions::Extension&);
 
   PendingExtensionInfo(
       const GURL& update_url,
@@ -26,7 +26,7 @@ class PendingExtensionInfo {
       ShouldAllowInstallPredicate should_allow_install,
       bool is_from_sync,
       bool install_silently,
-      Extension::Location install_source);
+      extensions::Extension::Location install_source);
 
   // Required for STL container membership.  Should not be used directly.
   PendingExtensionInfo();
@@ -40,12 +40,14 @@ class PendingExtensionInfo {
   // If not, the extension is discarded. This allows creators of
   // PendingExtensionInfo objects to ensure that extensions meet some criteria
   // that can only be tested once the extension is unpacked.
-  bool ShouldAllowInstall(const Extension& extension) const {
+  bool ShouldAllowInstall(const extensions::Extension& extension) const {
     return should_allow_install_(extension);
   }
   bool is_from_sync() const { return is_from_sync_; }
   bool install_silently() const { return install_silently_; }
-  Extension::Location install_source() const { return install_source_; }
+  extensions::Extension::Location install_source() const {
+        return install_source_;
+  }
 
  private:
   GURL update_url_;
@@ -58,7 +60,7 @@ class PendingExtensionInfo {
 
   bool is_from_sync_;  // This update check was initiated from sync.
   bool install_silently_;
-  Extension::Location install_source_;
+  extensions::Extension::Location install_source_;
 
   FRIEND_TEST_ALL_PREFIXES(ExtensionServiceTest, AddPendingExtensionFromSync);
 };
diff --git a/chrome/browser/extensions/pending_extension_manager.cc b/chrome/browser/extensions/pending_extension_manager.cc
index 8677111..c2f9c60 100644
--- a/chrome/browser/extensions/pending_extension_manager.cc
+++ b/chrome/browser/extensions/pending_extension_manager.cc
@@ -11,6 +11,7 @@
 #include "content/public/browser/browser_thread.h"
 
 using content::BrowserThread;
+using extensions::Extension;
 
 namespace {
 
diff --git a/chrome/browser/extensions/pending_extension_manager.h b/chrome/browser/extensions/pending_extension_manager.h
index 4aeecbf..8668892 100644
--- a/chrome/browser/extensions/pending_extension_manager.h
+++ b/chrome/browser/extensions/pending_extension_manager.h
@@ -74,14 +74,14 @@ class PendingExtensionManager {
   // to be fetched, installed, and activated.
   bool AddFromExternalUpdateUrl(const std::string& id,
                                 const GURL& update_url,
-                                Extension::Location location);
+                                extensions::Extension::Location location);
 
   // Add a pending extension record for an external CRX file.
   // Return true if the CRX should be installed, false if an existing
   // pending record overrides it.
   bool AddFromExternalFile(
       const std::string& id,
-      Extension::Location location,
+      extensions::Extension::Location location,
       const Version& version);
 
   // Get the set of pending IDs that should be installed from an update URL.
@@ -102,7 +102,7 @@ class PendingExtensionManager {
       PendingExtensionInfo::ShouldAllowInstallPredicate should_allow_install,
       bool is_from_sync,
       bool install_silently,
-      Extension::Location install_source);
+      extensions::Extension::Location install_source);
 
   // Add a pending extension record directly.  Used for unit tests that need
   // to set an inital state. Use friendship to allow the tests to call this
diff --git a/chrome/browser/extensions/permissions_updater.h b/chrome/browser/extensions/permissions_updater.h
index 0640f2d..863e620 100644
--- a/chrome/browser/extensions/permissions_updater.h
+++ b/chrome/browser/extensions/permissions_updater.h
@@ -10,16 +10,18 @@
 
 #include "base/memory/ref_counted.h"
 
-namespace base {
-class DictionaryValue;
-}
-class Extension;
 class ExtensionPermissionSet;
 class ExtensionPrefs;
 class Profile;
 
+namespace base {
+class DictionaryValue;
+}
+
 namespace extensions {
 
+class Extension;
+
 // Updates an Extension's active and granted permissions in persistent storage
 // and notifies interested parties of the changes.
 class PermissionsUpdater {
diff --git a/chrome/browser/extensions/platform_app_browsertest.cc b/chrome/browser/extensions/platform_app_browsertest.cc
index 44f615a..4fb84ae 100644
--- a/chrome/browser/extensions/platform_app_browsertest.cc
+++ b/chrome/browser/extensions/platform_app_browsertest.cc
@@ -65,7 +65,7 @@ class PlatformAppBrowserTest : public ExtensionApiTest {
         AppendASCII(name)));
 
     ExtensionService* service = browser()->profile()->GetExtensionService();
-    const Extension* extension = service->GetExtensionById(
+    const extensions::Extension* extension = service->GetExtensionById(
         last_loaded_extension_id_, false);
     EXPECT_TRUE(extension);
 
diff --git a/chrome/browser/extensions/process_management_browsertest.cc b/chrome/browser/extensions/process_management_browsertest.cc
index 1639161f..9436e14 100644
--- a/chrome/browser/extensions/process_management_browsertest.cc
+++ b/chrome/browser/extensions/process_management_browsertest.cc
@@ -63,7 +63,7 @@ IN_PROC_BROWSER_TEST_F(ProcessManagementTest, ProcessOverflow) {
   base_url = base_url.ReplaceComponents(replace_host);
 
   // Load an extension before adding tabs.
-  const Extension* extension1 = LoadExtension(
+  const extensions::Extension* extension1 = LoadExtension(
       test_data_dir_.AppendASCII("api_test/browser_action/basics"));
   ASSERT_TRUE(extension1);
   GURL extension1_url = extension1->url();
@@ -101,7 +101,7 @@ IN_PROC_BROWSER_TEST_F(ProcessManagementTest, ProcessOverflow) {
       NEW_FOREGROUND_TAB, ui_test_utils::BROWSER_TEST_WAIT_FOR_NAVIGATION);
 
   // Load another extension.
-  const Extension* extension2 = LoadExtension(
+  const extensions::Extension* extension2 = LoadExtension(
       test_data_dir_.AppendASCII("api_test/browser_action/close_background"));
   ASSERT_TRUE(extension2);
   GURL extension2_url = extension2->url();
diff --git a/chrome/browser/extensions/sandboxed_extension_unpacker.cc b/chrome/browser/extensions/sandboxed_extension_unpacker.cc
index 52cbebf..a919450 100644
--- a/chrome/browser/extensions/sandboxed_extension_unpacker.cc
+++ b/chrome/browser/extensions/sandboxed_extension_unpacker.cc
@@ -34,6 +34,7 @@
 
 using content::BrowserThread;
 using content::UtilityProcessHost;
+using extensions::Extension;
 
 // The following macro makes histograms that record the length of paths
 // in this file much easier to read.
diff --git a/chrome/browser/extensions/sandboxed_extension_unpacker.h b/chrome/browser/extensions/sandboxed_extension_unpacker.h
index 696c4cd..d28b8ed 100644
--- a/chrome/browser/extensions/sandboxed_extension_unpacker.h
+++ b/chrome/browser/extensions/sandboxed_extension_unpacker.h
@@ -15,8 +15,6 @@
 #include "content/public/browser/browser_thread.h"
 #include "content/public/browser/utility_process_host_client.h"
 
-class Extension;
-
 namespace base {
 class DictionaryValue;
 }
@@ -37,7 +35,7 @@ class SandboxedExtensionUnpackerClient
   virtual void OnUnpackSuccess(const FilePath& temp_dir,
                                const FilePath& extension_root,
                                const base::DictionaryValue* original_manifest,
-                               const Extension* extension) = 0;
+                               const extensions::Extension* extension) = 0;
   virtual void OnUnpackFailure(const string16& error) = 0;
 
  protected:
@@ -102,7 +100,7 @@ class SandboxedExtensionUnpacker : public content::UtilityProcessHostClient {
   // is done in a sandboxed subprocess. Otherwise, it is done in-process.
   SandboxedExtensionUnpacker(const FilePath& crx_path,
                              bool run_out_of_process,
-                             Extension::Location location,
+                             extensions::Extension::Location location,
                              int creation_flags,
                              SandboxedExtensionUnpackerClient* client);
 
@@ -233,7 +231,7 @@ class SandboxedExtensionUnpacker : public content::UtilityProcessHostClient {
   FilePath extension_root_;
 
   // Represents the extension we're unpacking.
-  scoped_refptr<Extension> extension_;
+  scoped_refptr<extensions::Extension> extension_;
 
   // Whether we've received a response from the utility process yet.
   bool got_response_;
@@ -249,7 +247,7 @@ class SandboxedExtensionUnpacker : public content::UtilityProcessHostClient {
   base::TimeTicks unpack_start_time_;
 
   // Location to use for the unpacked extension.
-  Extension::Location location_;
+  extensions::Extension::Location location_;
 
   // Creation flags to use for the extension.  These flags will be used
   // when calling Extenion::Create() by the crx installer.
diff --git a/chrome/browser/extensions/sandboxed_extension_unpacker_unittest.cc b/chrome/browser/extensions/sandboxed_extension_unpacker_unittest.cc
index 205f14f..47887e8 100644
--- a/chrome/browser/extensions/sandboxed_extension_unpacker_unittest.cc
+++ b/chrome/browser/extensions/sandboxed_extension_unpacker_unittest.cc
@@ -24,6 +24,7 @@ namespace errors = extension_manifest_errors;
 namespace keys = extension_manifest_keys;
 
 using content::BrowserThread;
+using extensions::Extension;
 using testing::_;
 using testing::Invoke;
 
diff --git a/chrome/browser/extensions/script_badge_controller.h b/chrome/browser/extensions/script_badge_controller.h
index 511ac86..436a404 100644
--- a/chrome/browser/extensions/script_badge_controller.h
+++ b/chrome/browser/extensions/script_badge_controller.h
@@ -16,13 +16,14 @@
 #include "chrome/browser/extensions/script_executor_impl.h"
 #include "content/public/browser/web_contents_observer.h"
 
-class Extension;
 class ExtensionAction;
 class ExtensionService;
 class TabContentsWrapper;
 
 namespace extensions {
 
+class Extension;
+
 // An ActionBoxController which corresponds to script badges, and implements
 // ScriptExecutor in order to show those scripts in the action box too.
 class ScriptBadgeController : public ActionBoxController,
diff --git a/chrome/browser/extensions/test_extension_prefs.cc b/chrome/browser/extensions/test_extension_prefs.cc
index fed319d..6ef8bf0 100644
--- a/chrome/browser/extensions/test_extension_prefs.cc
+++ b/chrome/browser/extensions/test_extension_prefs.cc
@@ -25,6 +25,7 @@
 #include "testing/gtest/include/gtest/gtest.h"
 
 using content::BrowserThread;
+using extensions::Extension;
 
 namespace {
 
diff --git a/chrome/browser/extensions/test_extension_prefs.h b/chrome/browser/extensions/test_extension_prefs.h
index 25862dd..dc35c42 100644
--- a/chrome/browser/extensions/test_extension_prefs.h
+++ b/chrome/browser/extensions/test_extension_prefs.h
@@ -38,20 +38,21 @@ class TestExtensionPrefs {
 
   // Creates a new Extension with the given name in our temp dir, adds it to
   // our ExtensionPrefs, and returns it.
-  scoped_refptr<Extension> AddExtension(std::string name);
+  scoped_refptr<extensions::Extension> AddExtension(std::string name);
 
   // As above, but the extension is an app.
-  scoped_refptr<Extension> AddApp(std::string name);
+  scoped_refptr<extensions::Extension> AddApp(std::string name);
 
   // Similar to AddExtension, but takes a dictionary with manifest values.
-  scoped_refptr<Extension> AddExtensionWithManifest(
-      const base::DictionaryValue& manifest, Extension::Location location);
+  scoped_refptr<extensions::Extension> AddExtensionWithManifest(
+      const base::DictionaryValue& manifest,
+      extensions::Extension::Location location);
 
   // Similar to AddExtension, but takes a dictionary with manifest values
   // and extension flags.
-  scoped_refptr<Extension> AddExtensionWithManifestAndFlags(
+  scoped_refptr<extensions::Extension> AddExtensionWithManifestAndFlags(
       const base::DictionaryValue& manifest,
-      Extension::Location location,
+      extensions::Extension::Location location,
       int extra_flags);
 
   // Similar to AddExtension, this adds a new test Extension. This is useful for
diff --git a/chrome/browser/extensions/test_extension_service.cc b/chrome/browser/extensions/test_extension_service.cc
index bab9ac9..6a8f1ea 100644
--- a/chrome/browser/extensions/test_extension_service.cc
+++ b/chrome/browser/extensions/test_extension_service.cc
@@ -8,6 +8,8 @@
 #include "sync/api/sync_error_factory.h"
 #include "testing/gtest/include/gtest/gtest.h"
 
+using extensions::Extension;
+
 TestExtensionService::~TestExtensionService() {}
 
 const ExtensionSet* TestExtensionService::extensions() const {
diff --git a/chrome/browser/extensions/test_extension_service.h b/chrome/browser/extensions/test_extension_service.h
index 699f88c..e445f20 100644
--- a/chrome/browser/extensions/test_extension_service.h
+++ b/chrome/browser/extensions/test_extension_service.h
@@ -14,6 +14,10 @@
 class CrxInstaller;
 class SyncErrorFactory;
 
+namespace extensions {
+class Extension;
+}
+
 // Implemention of ExtensionServiceInterface with default
 // implementations for methods that add failures.  You should subclass
 // this and override the methods you care about.
@@ -31,9 +35,9 @@ class TestExtensionService : public ExtensionServiceInterface {
       const FilePath& path,
       const GURL& download_url,
       CrxInstaller** out_crx_installer) OVERRIDE;
-  virtual const Extension* GetExtensionById(
+  virtual const extensions::Extension* GetExtensionById(
       const std::string& id, bool include_disabled) const OVERRIDE;
-  virtual const Extension* GetInstalledExtension(
+  virtual const extensions::Extension* GetInstalledExtension(
       const std::string& id) const OVERRIDE;
   virtual bool IsExtensionEnabled(
       const std::string& extension_id) const OVERRIDE;
@@ -58,13 +62,14 @@ class TestExtensionService : public ExtensionServiceInterface {
 
   virtual bool is_ready() OVERRIDE;
 
-  virtual void AddExtension(const Extension* extension) OVERRIDE;
+  virtual void AddExtension(const extensions::Extension* extension) OVERRIDE;
 
   virtual void UnloadExtension(
       const std::string& extension_id,
       extension_misc::UnloadedExtensionReason reason) OVERRIDE;
 
-  virtual void SyncExtensionChangeIfNeeded(const Extension& extension) OVERRIDE;
+  virtual void SyncExtensionChangeIfNeeded(
+      const extensions::Extension& extension) OVERRIDE;
 };
 
 #endif  // CHROME_BROWSER_EXTENSIONS_TEST_EXTENSION_SERVICE_H_
diff --git a/chrome/browser/extensions/theme_installed_infobar_delegate.cc b/chrome/browser/extensions/theme_installed_infobar_delegate.cc
index e6a9373..36f023b 100644
--- a/chrome/browser/extensions/theme_installed_infobar_delegate.cc
+++ b/chrome/browser/extensions/theme_installed_infobar_delegate.cc
@@ -23,7 +23,7 @@ ThemeInstalledInfoBarDelegate::ThemeInstalledInfoBarDelegate(
     InfoBarTabHelper* infobar_helper,
     ExtensionService* extension_service,
     ThemeService* theme_service,
-    const Extension* new_theme,
+    const extensions::Extension* new_theme,
     const std::string& previous_theme_id,
     bool previous_using_native_theme)
     : ConfirmInfoBarDelegate(infobar_helper),
@@ -38,7 +38,8 @@ ThemeInstalledInfoBarDelegate::ThemeInstalledInfoBarDelegate(
                  content::Source<ThemeService>(theme_service_));
 }
 
-bool ThemeInstalledInfoBarDelegate::MatchesTheme(const Extension* theme) const {
+bool ThemeInstalledInfoBarDelegate::MatchesTheme(
+    const extensions::Extension* theme) const {
   return theme && (theme->id() == theme_id_);
 }
 
@@ -51,7 +52,7 @@ ThemeInstalledInfoBarDelegate::~ThemeInstalledInfoBarDelegate() {
 
 bool ThemeInstalledInfoBarDelegate::Cancel() {
   if (!previous_theme_id_.empty()) {
-    const Extension* previous_theme =
+    const extensions::Extension* previous_theme =
         extension_service_->GetExtensionById(previous_theme_id_, true);
     if (previous_theme) {
       theme_service_->SetTheme(previous_theme);
diff --git a/chrome/browser/extensions/theme_installed_infobar_delegate.h b/chrome/browser/extensions/theme_installed_infobar_delegate.h
index 28cad72..3e7b0d1 100644
--- a/chrome/browser/extensions/theme_installed_infobar_delegate.h
+++ b/chrome/browser/extensions/theme_installed_infobar_delegate.h
@@ -13,10 +13,13 @@
 #include "content/public/browser/notification_observer.h"
 #include "content/public/browser/notification_registrar.h"
 
-class Extension;
 class ExtensionService;
 class ThemeService;
 
+namespace extensions {
+class Extension;
+}
+
 // When a user installs a theme, we display it immediately, but provide an
 // infobar allowing them to cancel.
 class ThemeInstalledInfoBarDelegate : public ConfirmInfoBarDelegate,
@@ -25,13 +28,13 @@ class ThemeInstalledInfoBarDelegate : public ConfirmInfoBarDelegate,
   ThemeInstalledInfoBarDelegate(InfoBarTabHelper* infobar_helper,
                                 ExtensionService* extension_service,
                                 ThemeService* theme_service,
-                                const Extension* new_theme,
+                                const extensions::Extension* new_theme,
                                 const std::string& previous_theme_id,
                                 bool previous_using_native_theme);
 
   // Returns true if the given theme is the same as the one associated with this
   // info bar.
-  bool MatchesTheme(const Extension* theme) const;
+  bool MatchesTheme(const extensions::Extension* theme) const;
 
  protected:
   virtual ~ThemeInstalledInfoBarDelegate();
diff --git a/chrome/browser/extensions/unpacked_installer.cc b/chrome/browser/extensions/unpacked_installer.cc
index 964a69e..39e5513 100644
--- a/chrome/browser/extensions/unpacked_installer.cc
+++ b/chrome/browser/extensions/unpacked_installer.cc
@@ -16,6 +16,7 @@
 #include "chrome/common/string_ordinal.h"
 
 using content::BrowserThread;
+using extensions::Extension;
 
 namespace {
 
diff --git a/chrome/browser/extensions/unpacked_installer.h b/chrome/browser/extensions/unpacked_installer.h
index 437e223..ad60d0a 100644
--- a/chrome/browser/extensions/unpacked_installer.h
+++ b/chrome/browser/extensions/unpacked_installer.h
@@ -12,11 +12,12 @@
 #include "base/memory/ref_counted.h"
 #include "base/memory/weak_ptr.h"
 
-class Extension;
 class ExtensionService;
 
 namespace extensions {
 
+class Extension;
+
 // Installs and loads an unpacked extension.
 // TODO(erikkay): It might be useful to be able to load a packed extension
 // (presumably into memory) without installing it.
diff --git a/chrome/browser/extensions/user_script_listener.cc b/chrome/browser/extensions/user_script_listener.cc
index 689e7e2..987323c 100644
--- a/chrome/browser/extensions/user_script_listener.cc
+++ b/chrome/browser/extensions/user_script_listener.cc
@@ -164,8 +164,9 @@ void UserScriptListener::ReplaceURLPatterns(void* profile_id,
   data.url_patterns = patterns;
 }
 
-void UserScriptListener::CollectURLPatterns(const Extension* extension,
-                                            URLPatterns* patterns) {
+void UserScriptListener::CollectURLPatterns(
+    const extensions::Extension* extension,
+    URLPatterns* patterns) {
   DCHECK(BrowserThread::CurrentlyOn(BrowserThread::UI));
 
   const UserScriptList& scripts = extension->content_scripts();
@@ -185,8 +186,8 @@ void UserScriptListener::Observe(int type,
   switch (type) {
     case chrome::NOTIFICATION_EXTENSION_LOADED: {
       Profile* profile = content::Source<Profile>(source).ptr();
-      const Extension* extension =
-          content::Details<const Extension>(details).ptr();
+      const extensions::Extension* extension =
+          content::Details<const extensions::Extension>(details).ptr();
       if (extension->content_scripts().empty())
         return;  // no new patterns from this extension.
 
@@ -202,8 +203,9 @@ void UserScriptListener::Observe(int type,
 
     case chrome::NOTIFICATION_EXTENSION_UNLOADED: {
       Profile* profile = content::Source<Profile>(source).ptr();
-      const Extension* unloaded_extension =
-          content::Details<UnloadedExtensionInfo>(details)->extension;
+      const extensions::Extension* unloaded_extension =
+          content::Details<extensions::UnloadedExtensionInfo>(
+              details)->extension;
       if (unloaded_extension->content_scripts().empty())
         return;  // no patterns to delete for this extension.
 
diff --git a/chrome/browser/extensions/user_script_listener.h b/chrome/browser/extensions/user_script_listener.h
index 15797bd..163b555 100644
--- a/chrome/browser/extensions/user_script_listener.h
+++ b/chrome/browser/extensions/user_script_listener.h
@@ -18,7 +18,6 @@
 #include "content/public/browser/notification_registrar.h"
 #include "webkit/glue/resource_type.h"
 
-class Extension;
 class GURL;
 class URLPattern;
 
@@ -26,6 +25,10 @@ namespace content {
 class ResourceThrottle;
 }
 
+namespace extensions {
+class Extension;
+}
+
 // This class handles delaying of resource loads that depend on unloaded user
 // scripts. For each request that comes in, we check if it depends on a user
 // script, and if so, whether that user script is ready; if not, we delay the
@@ -95,7 +98,8 @@ class UserScriptListener
 
   // Helper to collect the extension's user script URL patterns in a list and
   // return it.
-  void CollectURLPatterns(const Extension* extension, URLPatterns* patterns);
+  void CollectURLPatterns(const extensions::Extension* extension,
+                          URLPatterns* patterns);
 
   // content::NotificationObserver
   virtual void Observe(int type,
diff --git a/chrome/browser/extensions/user_script_listener_unittest.cc b/chrome/browser/extensions/user_script_listener_unittest.cc
index 7c0c808..38b628b 100644
--- a/chrome/browser/extensions/user_script_listener_unittest.cc
+++ b/chrome/browser/extensions/user_script_listener_unittest.cc
@@ -23,6 +23,7 @@
 
 using content::ResourceThrottle;
 using content::ResourceThrottleController;
+using extensions::Extension;
 
 namespace {
 
diff --git a/chrome/browser/extensions/user_script_master.cc b/chrome/browser/extensions/user_script_master.cc
index af152b4eb..a422139 100644
--- a/chrome/browser/extensions/user_script_master.cc
+++ b/chrome/browser/extensions/user_script_master.cc
@@ -350,8 +350,8 @@ void UserScriptMaster::Observe(int type,
       break;
     case chrome::NOTIFICATION_EXTENSION_LOADED: {
       // Add any content scripts inside the extension.
-      const Extension* extension =
-          content::Details<const Extension>(details).ptr();
+      const extensions::Extension* extension =
+          content::Details<const extensions::Extension>(details).ptr();
       extensions_info_[extension->id()] =
           ExtensionSet::ExtensionPathAndDefaultLocale(
               extension->path(), extension->default_locale());
@@ -369,8 +369,9 @@ void UserScriptMaster::Observe(int type,
     }
     case chrome::NOTIFICATION_EXTENSION_UNLOADED: {
       // Remove any content scripts.
-      const Extension* extension =
-          content::Details<UnloadedExtensionInfo>(details)->extension;
+      const extensions::Extension* extension =
+          content::Details<extensions::UnloadedExtensionInfo>(
+              details)->extension;
       extensions_info_.erase(extension->id());
       UserScriptList new_user_scripts;
       for (UserScriptList::iterator iter = user_scripts_.begin();
diff --git a/chrome/browser/extensions/webstore_inline_install_browsertest.cc b/chrome/browser/extensions/webstore_inline_install_browsertest.cc
index be7b279..e2a5d8a 100644
--- a/chrome/browser/extensions/webstore_inline_install_browsertest.cc
+++ b/chrome/browser/extensions/webstore_inline_install_browsertest.cc
@@ -94,8 +94,9 @@ IN_PROC_BROWSER_TEST_F(WebstoreInlineInstallTest, Install) {
 
   RunInlineInstallTest("runTest");
 
-  const Extension* extension = browser()->profile()->GetExtensionService()->
-      GetExtensionById("ecglahbcnmdpdciemllbhojghbkagdje", false);
+  const extensions::Extension* extension = browser()->profile()->
+      GetExtensionService()->GetExtensionById(
+          "ecglahbcnmdpdciemllbhojghbkagdje", false);
   EXPECT_TRUE(extension);
 }
 
diff --git a/chrome/browser/extensions/webstore_inline_installer.cc b/chrome/browser/extensions/webstore_inline_installer.cc
index 8b7df47..2fca0f2 100644
--- a/chrome/browser/extensions/webstore_inline_installer.cc
+++ b/chrome/browser/extensions/webstore_inline_installer.cc
@@ -163,7 +163,7 @@ WebstoreInlineInstaller::WebstoreInlineInstaller(WebContents* web_contents,
 void WebstoreInlineInstaller::BeginInstall() {
   AddRef(); // Balanced in CompleteInstall or WebContentsDestroyed.
 
-  if (!Extension::IdIsValid(id_)) {
+  if (!extensions::Extension::IdIsValid(id_)) {
     CompleteInstall(kInvalidWebstoreItemId);
     return;
   }
diff --git a/chrome/browser/extensions/webstore_inline_installer.h b/chrome/browser/extensions/webstore_inline_installer.h
index 9a8cd60..bd35456 100644
--- a/chrome/browser/extensions/webstore_inline_installer.h
+++ b/chrome/browser/extensions/webstore_inline_installer.h
@@ -21,6 +21,10 @@
 
 class SafeWebstoreResponseParser;
 
+namespace extensions {
+class Extension;
+}
+
 // Manages inline installs requested by a page (downloads and parses metadata
 // from the webstore, shows the install UI, starts the download once the user
 // confirms).  Clients must implement the WebstoreInlineInstaller::Delegate
@@ -127,7 +131,7 @@ class WebstoreInlineInstaller
   int rating_count_;
   scoped_ptr<DictionaryValue> webstore_data_;
   scoped_ptr<DictionaryValue> manifest_;
-  scoped_refptr<Extension> dummy_extension_;
+  scoped_refptr<extensions::Extension> dummy_extension_;
   SkBitmap icon_;
 
   DISALLOW_IMPLICIT_CONSTRUCTORS(WebstoreInlineInstaller);
diff --git a/chrome/browser/extensions/webstore_installer.cc b/chrome/browser/extensions/webstore_installer.cc
index b43c2c3..9b22133 100644
--- a/chrome/browser/extensions/webstore_installer.cc
+++ b/chrome/browser/extensions/webstore_installer.cc
@@ -46,6 +46,8 @@ using content::DownloadUrlParameters;
 
 namespace {
 
+using extensions::Extension;
+
 // Key used to attach the Approval to the DownloadItem.
 const char kApprovalKey[] = "extensions.webstore_installer";
 
diff --git a/chrome/browser/extensions/window_open_apitest.cc b/chrome/browser/extensions/window_open_apitest.cc
index 63a216e..1d2c3fd 100644
--- a/chrome/browser/extensions/window_open_apitest.cc
+++ b/chrome/browser/extensions/window_open_apitest.cc
@@ -226,7 +226,7 @@ IN_PROC_BROWSER_TEST_F(WindowOpenPanelTest,
         new ExtensionTestMessageListener(test_strings[i], false));
   }
 
-  const Extension* extension = LoadExtension(
+  const extensions::Extension* extension = LoadExtension(
       test_data_dir_.AppendASCII("window_open").AppendASCII(
           "close_panels_on_uninstall"));
   ASSERT_TRUE(extension);
diff --git a/chrome/browser/geolocation/chrome_geolocation_permission_context.cc b/chrome/browser/geolocation/chrome_geolocation_permission_context.cc
index 4d2465b..7d61875 100644
--- a/chrome/browser/geolocation/chrome_geolocation_permission_context.cc
+++ b/chrome/browser/geolocation/chrome_geolocation_permission_context.cc
@@ -604,7 +604,7 @@ void ChromeGeolocationPermissionContext::RequestGeolocationPermission(
 
   ExtensionService* extension_service = profile_->GetExtensionService();
   if (extension_service) {
-    const Extension* extension =
+    const extensions::Extension* extension =
         extension_service->extensions()->GetExtensionOrAppByURL(
             ExtensionURLInfo(
                 WebSecurityOrigin::createFromString(
diff --git a/chrome/browser/history/multipart_browsertest.cc b/chrome/browser/history/multipart_browsertest.cc
index ab0d6b1..42229aa 100644
--- a/chrome/browser/history/multipart_browsertest.cc
+++ b/chrome/browser/history/multipart_browsertest.cc
@@ -31,7 +31,7 @@ class MultipartResponseTest : public InProcessBrowserTest,
 
 IN_PROC_BROWSER_TEST_F(MultipartResponseTest, SingleVisit) {
   // Make sure that visiting a multipart/x-mixed-replace site only
-  // creates one entry in the visits table. 
+  // creates one entry in the visits table.
   ASSERT_TRUE(test_server()->Start());
 
   Observe(browser()->GetSelectedWebContents());
diff --git a/chrome/browser/infobars/infobar_extension_api.cc b/chrome/browser/infobars/infobar_extension_api.cc
index 3e9c427..6875e6d 100644
--- a/chrome/browser/infobars/infobar_extension_api.cc
+++ b/chrome/browser/infobars/infobar_extension_api.cc
@@ -22,6 +22,8 @@
 #include "content/public/browser/web_contents.h"
 #include "grit/generated_resources.h"
 
+using extensions::Extension;
+
 namespace {
 
 const char kHtmlPath[] = "path";
diff --git a/chrome/browser/intents/web_intents_registry.cc b/chrome/browser/intents/web_intents_registry.cc
index ff9c139..558d912 100644
--- a/chrome/browser/intents/web_intents_registry.cc
+++ b/chrome/browser/intents/web_intents_registry.cc
@@ -19,6 +19,8 @@
 #include "googleurl/src/gurl.h"
 #include "net/base/mime_util.h"
 
+using extensions::Extension;
+
 namespace {
 
 typedef WebIntentsRegistry::IntentServiceList IntentServiceList;
diff --git a/chrome/browser/intents/web_intents_registry.h b/chrome/browser/intents/web_intents_registry.h
index 2faa81c..7874e4f 100644
--- a/chrome/browser/intents/web_intents_registry.h
+++ b/chrome/browser/intents/web_intents_registry.h
@@ -16,6 +16,10 @@
 
 struct DefaultWebIntentService;
 
+namespace extensions {
+class Extension;
+}
+
 // Handles storing and retrieving of web intents services in the web database.
 // The registry provides filtering logic to retrieve specific types of services.
 class WebIntentsRegistry
@@ -107,7 +111,7 @@ class WebIntentsRegistry
   void CollapseIntents(IntentServiceList* services);
 
  private:
-   const Extension* ExtensionForURL(const std::string& url);
+   const extensions::Extension* ExtensionForURL(const std::string& url);
 
    struct IntentsQuery;
 
diff --git a/chrome/browser/intents/web_intents_registry_unittest.cc b/chrome/browser/intents/web_intents_registry_unittest.cc
index d1bc601..82673af 100644
--- a/chrome/browser/intents/web_intents_registry_unittest.cc
+++ b/chrome/browser/intents/web_intents_registry_unittest.cc
@@ -21,6 +21,7 @@
 #include "testing/gtest/include/gtest/gtest.h"
 
 using content::BrowserThread;
+using extensions::Extension;
 using webkit_glue::WebIntentServiceData;
 
 class MockExtensionService: public TestExtensionService {
diff --git a/chrome/browser/memory_details.cc b/chrome/browser/memory_details.cc
index 2a6015d..b739a23 100644
--- a/chrome/browser/memory_details.cc
+++ b/chrome/browser/memory_details.cc
@@ -43,6 +43,7 @@ using content::NavigationEntry;
 using content::RenderViewHost;
 using content::RenderWidgetHost;
 using content::WebContents;
+using extensions::Extension;
 
 // static
 std::string ProcessMemoryInformation::GetRendererTypeNameInEnglish(
diff --git a/chrome/browser/nacl_host/nacl_process_host.cc b/chrome/browser/nacl_host/nacl_process_host.cc
index e1faeba..300a271 100644
--- a/chrome/browser/nacl_host/nacl_process_host.cc
+++ b/chrome/browser/nacl_host/nacl_process_host.cc
@@ -411,7 +411,7 @@ void NaClProcessHost::OnNaClGdbAttached() {
 #endif
 
 FilePath NaClProcessHost::GetManifestPath() {
-  const Extension* extension = extension_info_map_->extensions()
+  const extensions::Extension* extension = extension_info_map_->extensions()
       .GetExtensionOrAppByURL(ExtensionURLInfo(manifest_url_));
   if (extension != NULL && manifest_url_.SchemeIs(chrome::kExtensionScheme)) {
     std::string path = manifest_url_.path();
diff --git a/chrome/browser/notifications/desktop_notification_service.cc b/chrome/browser/notifications/desktop_notification_service.cc
index ff35176..f8527ab 100644
--- a/chrome/browser/notifications/desktop_notification_service.cc
+++ b/chrome/browser/notifications/desktop_notification_service.cc
@@ -270,8 +270,8 @@ void DesktopNotificationService::Observe(
   if (type == chrome::NOTIFICATION_EXTENSION_UNLOADED) {
     // Remove all notifications currently shown or queued by the extension
     // which was unloaded.
-    const Extension* extension =
-        content::Details<UnloadedExtensionInfo>(details)->extension;
+    const extensions::Extension* extension =
+        content::Details<extensions::UnloadedExtensionInfo>(details)->extension;
     if (extension)
       GetUIManager()->CancelAllBySourceOrigin(extension->url());
   } else if (type == chrome::NOTIFICATION_PROFILE_DESTROYED) {
@@ -408,7 +408,7 @@ string16 DesktopNotificationService::DisplayNameForOrigin(
   if (origin.SchemeIs(chrome::kExtensionScheme)) {
     ExtensionService* extension_service = profile_->GetExtensionService();
     if (extension_service) {
-      const Extension* extension =
+      const extensions::Extension* extension =
           extension_service->extensions()->GetExtensionOrAppByURL(
               ExtensionURLInfo(
                   WebSecurityOrigin::createFromString(
diff --git a/chrome/browser/notifications/notification_options_menu_model.cc b/chrome/browser/notifications/notification_options_menu_model.cc
index 33c1f00..b598ac8 100644
--- a/chrome/browser/notifications/notification_options_menu_model.cc
+++ b/chrome/browser/notifications/notification_options_menu_model.cc
@@ -124,7 +124,7 @@ NotificationOptionsMenuModel::NotificationOptionsMenuModel(Balloon* balloon)
   if (origin.SchemeIs(chrome::kExtensionScheme)) {
     ExtensionService* extension_service =
         balloon_->profile()->GetExtensionService();
-    const Extension* extension =
+    const extensions::Extension* extension =
         extension_service->extensions()->GetExtensionOrAppByURL(
             ExtensionURLInfo(origin));
     // We get back no extension here when we show the notification after
@@ -176,7 +176,7 @@ string16 NotificationOptionsMenuModel::GetLabelForCommandId(int command_id)
     if (origin.SchemeIs(chrome::kExtensionScheme)) {
       ExtensionService* extension_service =
           balloon_->profile()->GetExtensionService();
-      const Extension* extension =
+      const extensions::Extension* extension =
           extension_service->extensions()->GetExtensionOrAppByURL(
               ExtensionURLInfo(origin));
       if (extension) {
@@ -234,14 +234,14 @@ void NotificationOptionsMenuModel::ExecuteCommand(int command_id) {
         service->GrantPermission(origin);
       break;
     case kToggleExtensionCommand: {
-      const Extension* extension =
+      const extensions::Extension* extension =
           extension_service->extensions()->GetExtensionOrAppByURL(
               ExtensionURLInfo(origin));
       if (extension) {
         const std::string& id = extension->id();
         if (extension_service->IsExtensionEnabled(id))
           extension_service->DisableExtension(
-              id, Extension::DISABLE_USER_ACTION);
+              id, extensions::Extension::DISABLE_USER_ACTION);
         else
           extension_service->EnableExtension(id);
       }
diff --git a/chrome/browser/password_manager/password_store_factory.h b/chrome/browser/password_manager/password_store_factory.h
index faadb87..14b0d37 100644
--- a/chrome/browser/password_manager/password_store_factory.h
+++ b/chrome/browser/password_manager/password_store_factory.h
@@ -11,7 +11,6 @@
 #include "chrome/browser/profiles/refcounted_profile_keyed_service_factory.h"
 
 class PasswordStore;
-class Extension;
 class Profile;
 
 #if !defined(OS_MACOSX) && !defined(OS_CHROMEOS) && defined(OS_POSIX)
diff --git a/chrome/browser/policy/app_pack_updater.cc b/chrome/browser/policy/app_pack_updater.cc
index 2de085d..b0f20bf 100644
--- a/chrome/browser/policy/app_pack_updater.cc
+++ b/chrome/browser/policy/app_pack_updater.cc
@@ -278,7 +278,7 @@ void AppPackUpdater::BlockingCheckCacheInternal(
       }
     }
 
-    if (!Extension::IdIsValid(id)) {
+    if (!extensions::Extension::IdIsValid(id)) {
       LOG(ERROR) << "Bad AppPack extension id in cache: " << id;
       id.clear();
     } else if (!ContainsKey(*valid_ids, id)) {
diff --git a/chrome/browser/policy/configuration_policy_handler.cc b/chrome/browser/policy/configuration_policy_handler.cc
index 7dd32dd..023cb1d 100644
--- a/chrome/browser/policy/configuration_policy_handler.cc
+++ b/chrome/browser/policy/configuration_policy_handler.cc
@@ -265,7 +265,8 @@ bool ExtensionListPolicyHandler::CheckAndGetList(
                        ValueTypeToString(base::Value::TYPE_STRING));
       return false;
     }
-    if (!(allow_wildcards_ && id == "*") && !Extension::IdIsValid(id)) {
+    if (!(allow_wildcards_ && id == "*") &&
+        !extensions::Extension::IdIsValid(id)) {
       errors->AddError(policy_name(),
                        entry - list_value->begin(),
                        IDS_POLICY_VALUE_FORMAT_ERROR);
diff --git a/chrome/browser/profiles/off_the_record_profile_impl.cc b/chrome/browser/profiles/off_the_record_profile_impl.cc
index 533c192..a7017e5 100644
--- a/chrome/browser/profiles/off_the_record_profile_impl.cc
+++ b/chrome/browser/profiles/off_the_record_profile_impl.cc
@@ -266,7 +266,7 @@ net::URLRequestContextGetter*
     OffTheRecordProfileImpl::GetRequestContextForRenderProcess(
         int renderer_child_id) {
   if (GetExtensionService()) {
-    const Extension* installed_app = GetExtensionService()->
+    const extensions::Extension* installed_app = GetExtensionService()->
         GetInstalledAppForRenderer(renderer_child_id);
     if (installed_app != NULL && installed_app->is_storage_isolated()) {
       return GetRequestContextForIsolatedApp(installed_app->id());
diff --git a/chrome/browser/profiles/profile.h b/chrome/browser/profiles/profile.h
index a08a48b..8d75eee 100644
--- a/chrome/browser/profiles/profile.h
+++ b/chrome/browser/profiles/profile.h
@@ -21,7 +21,6 @@ class AutocompleteClassifier;
 class BookmarkModel;
 class ChromeAppCacheService;
 class ChromeURLDataManager;
-class Extension;
 class ExtensionEventRouter;
 class ExtensionProcessManager;
 class ExtensionService;
@@ -39,28 +38,29 @@ class UserScriptMaster;
 class VisitedLinkMaster;
 class WebDataService;
 
+namespace android {
+class TabContentsProvider;
+}
+
 namespace base {
 class Time;
 }
 
+namespace chrome_browser_net {
+class Predictor;
+}
+
 namespace chromeos {
 class LibCrosServiceLibraryImpl;
 class ResetDefaultProxyConfigServiceTask;
 }
 
-namespace chrome_browser_net {
-class Predictor;
-}
 
 namespace content {
 class SpeechRecognitionPreferences;
 class WebUI;
 }
 
-namespace android {
-class TabContentsProvider;
-}
-
 namespace fileapi {
 class FileSystemContext;
 }
diff --git a/chrome/browser/profiles/profile_impl.cc b/chrome/browser/profiles/profile_impl.cc
index 9585dd0..1c1d3a6 100644
--- a/chrome/browser/profiles/profile_impl.cc
+++ b/chrome/browser/profiles/profile_impl.cc
@@ -717,7 +717,7 @@ net::URLRequestContextGetter* ProfileImpl::GetRequestContextForRenderProcess(
   ExtensionService* extension_service =
       ExtensionSystem::Get(this)->extension_service();
   if (extension_service) {
-    const Extension* installed_app = extension_service->
+    const extensions::Extension* installed_app = extension_service->
         GetInstalledAppForRenderer(renderer_child_id);
     if (installed_app != NULL && installed_app->is_storage_isolated()) {
       return GetRequestContextForIsolatedApp(installed_app->id());
diff --git a/chrome/browser/renderer_host/chrome_render_message_filter.cc b/chrome/browser/renderer_host/chrome_render_message_filter.cc
index 1b46e85..8a9d16c 100644
--- a/chrome/browser/renderer_host/chrome_render_message_filter.cc
+++ b/chrome/browser/renderer_host/chrome_render_message_filter.cc
@@ -27,6 +27,7 @@
 #include "chrome/browser/task_manager/task_manager.h"
 #include "chrome/common/chrome_notification_types.h"
 #include "chrome/common/chrome_switches.h"
+#include "chrome/common/extensions/extension.h"
 #include "chrome/common/extensions/extension_file_util.h"
 #include "chrome/common/extensions/extension_message_bundle.h"
 #include "chrome/common/extensions/extension_messages.h"
@@ -304,7 +305,7 @@ void ChromeRenderMessageFilter::OpenChannelToTabOnUIThread(
 
 void ChromeRenderMessageFilter::OnGetExtensionMessageBundle(
     const std::string& extension_id, IPC::Message* reply_msg) {
-  const Extension* extension =
+  const extensions::Extension* extension =
       extension_info_map_->extensions().GetByID(extension_id);
   FilePath extension_path;
   std::string default_locale;
diff --git a/chrome/browser/renderer_host/chrome_render_view_host_observer.cc b/chrome/browser/renderer_host/chrome_render_view_host_observer.cc
index a064284..25198a0 100644
--- a/chrome/browser/renderer_host/chrome_render_view_host_observer.cc
+++ b/chrome/browser/renderer_host/chrome_render_view_host_observer.cc
@@ -23,6 +23,7 @@
 using content::ChildProcessSecurityPolicy;
 using content::RenderViewHost;
 using content::SiteInstance;
+using extensions::Extension;
 
 ChromeRenderViewHostObserver::ChromeRenderViewHostObserver(
     RenderViewHost* render_view_host, chrome_browser_net::Predictor* predictor)
diff --git a/chrome/browser/renderer_host/chrome_render_view_host_observer.h b/chrome/browser/renderer_host/chrome_render_view_host_observer.h
index 3d43e53..0092ba1 100644
--- a/chrome/browser/renderer_host/chrome_render_view_host_observer.h
+++ b/chrome/browser/renderer_host/chrome_render_view_host_observer.h
@@ -8,12 +8,15 @@
 
 #include "content/public/browser/render_view_host_observer.h"
 
+class Profile;
+
 namespace chrome_browser_net {
 class Predictor;
 }
 
+namespace extensions {
 class Extension;
-class Profile;
+}
 
 // This class holds the Chrome specific parts of RenderViewHost, and has the
 // same lifetime.
@@ -37,7 +40,7 @@ class ChromeRenderViewHostObserver : public content::RenderViewHostObserver {
    // created by a RenderViewHost.
   void InitRenderViewForExtensions();
   // Gets the extension or app (if any) that is associated with the RVH.
-  const Extension* GetExtension();
+  const extensions::Extension* GetExtension();
   // Cleans up when a RenderViewHost is removed, or on destruction.
   void RemoveRenderViewHostForExtensions(content::RenderViewHost* rvh);
   void OnFocusedEditableNodeTouched();
diff --git a/chrome/browser/search_engines/template_url_service.cc b/chrome/browser/search_engines/template_url_service.cc
index 27e123c..b472533 100644
--- a/chrome/browser/search_engines/template_url_service.cc
+++ b/chrome/browser/search_engines/template_url_service.cc
@@ -436,7 +436,8 @@ void TemplateURLService::RemoveAutoGeneratedForOriginBetween(
 }
 
 
-void TemplateURLService::RegisterExtensionKeyword(const Extension* extension) {
+void TemplateURLService::RegisterExtensionKeyword(
+    const extensions::Extension* extension) {
   // TODO(mpcomplete): disable the keyword when the extension is disabled.
   if (extension->omnibox_keyword().empty())
     return;
@@ -460,7 +461,7 @@ void TemplateURLService::RegisterExtensionKeyword(const Extension* extension) {
 }
 
 void TemplateURLService::UnregisterExtensionKeyword(
-    const Extension* extension) {
+    const extensions::Extension* extension) {
   if (loaded_) {
     TemplateURL* url = GetTemplateURLForExtension(extension);
     if (url)
@@ -474,7 +475,7 @@ void TemplateURLService::UnregisterExtensionKeyword(
 }
 
 TemplateURL* TemplateURLService::GetTemplateURLForExtension(
-    const Extension* extension) {
+    const extensions::Extension* extension) {
   for (TemplateURLVector::const_iterator i = template_urls_.begin();
        i != template_urls_.end(); ++i) {
     if ((*i)->IsExtensionKeyword() &&
@@ -1397,7 +1398,7 @@ void TemplateURLService::NotifyLoaded() {
 
   for (PendingExtensionIDs::const_iterator i(pending_extension_ids_.begin());
        i != pending_extension_ids_.end(); ++i) {
-    const Extension* extension =
+    const extensions::Extension* extension =
         profile_->GetExtensionService()->GetExtensionById(*i, true);
     if (extension)
       RegisterExtensionKeyword(extension);
diff --git a/chrome/browser/search_engines/template_url_service.h b/chrome/browser/search_engines/template_url_service.h
index 96338c6..b4a9f56 100644
--- a/chrome/browser/search_engines/template_url_service.h
+++ b/chrome/browser/search_engines/template_url_service.h
@@ -24,7 +24,6 @@
 #include "sync/api/sync_change.h"
 #include "sync/api/syncable_service.h"
 
-class Extension;
 class GURL;
 class PrefService;
 class Profile;
@@ -34,6 +33,10 @@ class SyncData;
 class SyncErrorFactory;
 class TemplateURLServiceObserver;
 
+namespace extensions {
+class Extension;
+}
+
 namespace history {
 struct URLVisitedDetails;
 }
@@ -174,16 +177,17 @@ class TemplateURLService : public WebDataServiceConsumer,
   // If the given extension has an omnibox keyword, adds a TemplateURL for that
   // keyword. Only 1 keyword is allowed for a given extension. If the keyword
   // already exists for this extension, does nothing.
-  void RegisterExtensionKeyword(const Extension* extension);
+  void RegisterExtensionKeyword(const extensions::Extension* extension);
 
   // Removes the TemplateURL containing the keyword for the given extension,
   // if any.
-  void UnregisterExtensionKeyword(const Extension* extension);
+  void UnregisterExtensionKeyword(const extensions::Extension* extension);
 
   // Returns the TemplateURL associated with the keyword for this extension.
   // This works by checking the extension ID, not the keyword, so it will work
   // even if the user changed the keyword.
-  TemplateURL* GetTemplateURLForExtension(const Extension* extension);
+  TemplateURL* GetTemplateURLForExtension(
+      const extensions::Extension* extension);
 
   // Returns the set of URLs describing the keywords. The elements are owned
   // by TemplateURLService and should not be deleted.
diff --git a/chrome/browser/sessions/tab_restore_service.cc b/chrome/browser/sessions/tab_restore_service.cc
index 7d66033..a6ed52f 100644
--- a/chrome/browser/sessions/tab_restore_service.cc
+++ b/chrome/browser/sessions/tab_restore_service.cc
@@ -537,7 +537,7 @@ void TabRestoreService::PopulateTab(Tab* tab,
           controller->GetWebContents());
   // wrapper is NULL in some browser tests.
   if (wrapper) {
-    const Extension* extension =
+    const extensions::Extension* extension =
         wrapper->extension_tab_helper()->extension_app();
     if (extension)
       tab->extension_app_id = extension->id();
diff --git a/chrome/browser/speech/extension_api/tts_engine_extension_api.cc b/chrome/browser/speech/extension_api/tts_engine_extension_api.cc
index ffaf83d..62a1c6e 100644
--- a/chrome/browser/speech/extension_api/tts_engine_extension_api.cc
+++ b/chrome/browser/speech/extension_api/tts_engine_extension_api.cc
@@ -15,6 +15,8 @@
 #include "chrome/browser/speech/extension_api/tts_extension_api_controller.h"
 #include "chrome/common/extensions/extension.h"
 
+using extensions::Extension;
+
 namespace constants = tts_extension_api_constants;
 
 namespace events {
diff --git a/chrome/browser/speech/extension_api/tts_engine_extension_api.h b/chrome/browser/speech/extension_api/tts_engine_extension_api.h
index eea8aa8..c8653cb 100644
--- a/chrome/browser/speech/extension_api/tts_engine_extension_api.h
+++ b/chrome/browser/speech/extension_api/tts_engine_extension_api.h
@@ -9,13 +9,16 @@
 #include "base/memory/singleton.h"
 #include "chrome/browser/extensions/extension_function.h"
 
-class Extension;
 class Utterance;
 
 namespace base {
 class ListValue;
 }
 
+namespace extensions {
+class Extension;
+}
+
 // Return a list of all available voices registered by extensions.
 void GetExtensionVoices(Profile* profile, base::ListValue* result_voices);
 
@@ -25,13 +28,13 @@ void GetExtensionVoices(Profile* profile, base::ListValue* result_voices);
 // the index of the voice within the extension in |voice_index| and
 // return true.
 bool GetMatchingExtensionVoice(Utterance* utterance,
-                               const Extension** matching_extension,
+                               const extensions::Extension** matching_extension,
                                size_t* voice_index);
 
 // Speak the given utterance by sending an event to the given TTS engine
 // extension voice.
 void ExtensionTtsEngineSpeak(Utterance* utterance,
-                             const Extension* extension,
+                             const extensions::Extension* extension,
                              size_t voice_index);
 
 // Stop speaking the given utterance by sending an event to the extension
diff --git a/chrome/browser/speech/extension_api/tts_extension_api_controller.cc b/chrome/browser/speech/extension_api/tts_extension_api_controller.cc
index 6663ef6..0d20674 100644
--- a/chrome/browser/speech/extension_api/tts_extension_api_controller.cc
+++ b/chrome/browser/speech/extension_api/tts_extension_api_controller.cc
@@ -172,7 +172,7 @@ void ExtensionTtsController::SpeakOrEnqueue(Utterance* utterance) {
 }
 
 void ExtensionTtsController::SpeakNow(Utterance* utterance) {
-  const Extension* extension;
+  const extensions::Extension* extension;
   size_t voice_index;
   if (GetMatchingExtensionVoice(utterance, &extension, &voice_index)) {
     current_utterance_ = utterance;
diff --git a/chrome/browser/speech/extension_api/tts_extension_api_controller.h b/chrome/browser/speech/extension_api/tts_extension_api_controller.h
index 098271d..b374d50 100644
--- a/chrome/browser/speech/extension_api/tts_extension_api_controller.h
+++ b/chrome/browser/speech/extension_api/tts_extension_api_controller.h
@@ -14,7 +14,6 @@
 #include "base/memory/singleton.h"
 #include "googleurl/src/gurl.h"
 
-class Extension;
 class ExtensionTtsPlatformImpl;
 class Profile;
 
diff --git a/chrome/browser/speech/speech_input_extension_manager.cc b/chrome/browser/speech/speech_input_extension_manager.cc
index 67ab90c..047f1de 100644
--- a/chrome/browser/speech/speech_input_extension_manager.cc
+++ b/chrome/browser/speech/speech_input_extension_manager.cc
@@ -183,7 +183,8 @@ void SpeechInputExtensionManager::Observe(int type,
     const content::NotificationDetails& details) {
   if (type == chrome::NOTIFICATION_EXTENSION_UNLOADED) {
     ExtensionUnloaded(
-        content::Details<UnloadedExtensionInfo>(details)->extension->id());
+        content::Details<extensions::UnloadedExtensionInfo>(details)->
+            extension->id());
   } else {
     NOTREACHED();
   }
@@ -319,7 +320,7 @@ void SpeechInputExtensionManager::DidStartReceivingAudioOnUIThread() {
   VLOG(1) << "State changed to recording";
   state_ = kRecording;
 
-  const Extension* extension = profile_->GetExtensionService()->
+  const extensions::Extension* extension = profile_->GetExtensionService()->
       GetExtensionById(extension_id_in_use_, true);
   DCHECK(extension);
 
diff --git a/chrome/browser/speech/speech_input_extension_manager.h b/chrome/browser/speech/speech_input_extension_manager.h
index 4ef6b82..3923506 100644
--- a/chrome/browser/speech/speech_input_extension_manager.h
+++ b/chrome/browser/speech/speech_input_extension_manager.h
@@ -15,7 +15,6 @@
 #include "content/public/browser/notification_observer.h"
 #include "content/public/browser/speech_recognition_event_listener.h"
 
-class Extension;
 class Profile;
 class SpeechRecognitionTrayIconController;
 
diff --git a/chrome/browser/sync/glue/chrome_extensions_activity_monitor.cc b/chrome/browser/sync/glue/chrome_extensions_activity_monitor.cc
index 1b30f72..17ec604 100644
--- a/chrome/browser/sync/glue/chrome_extensions_activity_monitor.cc
+++ b/chrome/browser/sync/glue/chrome_extensions_activity_monitor.cc
@@ -51,7 +51,8 @@ void ChromeExtensionsActivityMonitor::Observe(
     const content::NotificationDetails& details) {
   base::AutoLock lock(records_lock_);
   DCHECK(BrowserThread::CurrentlyOn(BrowserThread::UI));
-  const Extension* extension = content::Source<const Extension>(source).ptr();
+  const extensions::Extension* extension =
+      content::Source<const extensions::Extension>(source).ptr();
   const BookmarksFunction* f =
       content::Details<const BookmarksFunction>(details).ptr();
   if (f->name() == "bookmarks.update" ||
diff --git a/chrome/browser/sync/glue/chrome_extensions_activity_monitor_unittest.cc b/chrome/browser/sync/glue/chrome_extensions_activity_monitor_unittest.cc
index 8456094..66253e5 100644
--- a/chrome/browser/sync/glue/chrome_extensions_activity_monitor_unittest.cc
+++ b/chrome/browser/sync/glue/chrome_extensions_activity_monitor_unittest.cc
@@ -17,6 +17,8 @@
 #include "content/test/test_browser_thread.h"
 #include "testing/gtest/include/gtest/gtest.h"
 
+using extensions::Extension;
+
 namespace browser_sync {
 
 namespace {
diff --git a/chrome/browser/sync/glue/theme_util.cc b/chrome/browser/sync/glue/theme_util.cc
index 7f0f00c..5ce8132 100644
--- a/chrome/browser/sync/glue/theme_util.cc
+++ b/chrome/browser/sync/glue/theme_util.cc
@@ -17,6 +17,8 @@
 #include "googleurl/src/gurl.h"
 #include "sync/protocol/theme_specifics.pb.h"
 
+using extensions::Extension;
+
 namespace browser_sync {
 
 const char kCurrentThemeClientTag[] = "current_theme";
diff --git a/chrome/browser/sync/glue/theme_util.h b/chrome/browser/sync/glue/theme_util.h
index 988b39d..a502b73 100644
--- a/chrome/browser/sync/glue/theme_util.h
+++ b/chrome/browser/sync/glue/theme_util.h
@@ -6,9 +6,12 @@
 #define CHROME_BROWSER_SYNC_GLUE_THEME_UTIL_H_
 #pragma once
 
-class Extension;
 class Profile;
 
+namespace extensions {
+class Extension;
+}
+
 namespace sync_pb {
 class ThemeSpecifics;
 }  // sync_pb
@@ -41,7 +44,7 @@ void GetThemeSpecificsFromCurrentTheme(
 
 // Exposed only for testing.
 void GetThemeSpecificsFromCurrentThemeHelper(
-    const Extension* current_theme,
+    const extensions::Extension* current_theme,
     bool is_system_theme_distinct_from_default_theme,
     bool use_system_theme_by_default,
     sync_pb::ThemeSpecifics* theme_specifics);
diff --git a/chrome/browser/sync/glue/theme_util_unittest.cc b/chrome/browser/sync/glue/theme_util_unittest.cc
index c895983..7aede1e 100644
--- a/chrome/browser/sync/glue/theme_util_unittest.cc
+++ b/chrome/browser/sync/glue/theme_util_unittest.cc
@@ -16,6 +16,8 @@
 #include "testing/gmock/include/gmock/gmock.h"
 #include "testing/gtest/include/gtest/gtest.h"
 
+using extensions::Extension;
+
 namespace browser_sync {
 
 namespace {
diff --git a/chrome/browser/sync/test/integration/apps_helper.cc b/chrome/browser/sync/test/integration/apps_helper.cc
index dea553d..a73c17d 100644
--- a/chrome/browser/sync/test/integration/apps_helper.cc
+++ b/chrome/browser/sync/test/integration/apps_helper.cc
@@ -42,7 +42,9 @@ bool AllProfilesHaveSameAppsAsVerifier() {
 
 std::string InstallApp(Profile* profile, int index) {
   return SyncExtensionHelper::GetInstance()->InstallExtension(
-      profile, CreateFakeAppName(index), Extension::TYPE_HOSTED_APP);
+      profile,
+      CreateFakeAppName(index),
+      extensions::Extension::TYPE_HOSTED_APP);
 }
 
 std::string InstallAppForAllProfiles(int index) {
@@ -78,7 +80,7 @@ void IncognitoDisableApp(Profile* profile, int index) {
 
 void InstallAppsPendingForSync(Profile* profile) {
   SyncExtensionHelper::GetInstance()->InstallExtensionsPendingForSync(
-      profile, Extension::TYPE_HOSTED_APP);
+      profile, extensions::Extension::TYPE_HOSTED_APP);
 }
 
 StringOrdinal GetPageOrdinalForApp(Profile* profile,
diff --git a/chrome/browser/sync/test/integration/extensions_helper.cc b/chrome/browser/sync/test/integration/extensions_helper.cc
index e6873b3..66fd789 100644
--- a/chrome/browser/sync/test/integration/extensions_helper.cc
+++ b/chrome/browser/sync/test/integration/extensions_helper.cc
@@ -51,7 +51,9 @@ bool AllProfilesHaveSameExtensions() {
 
 std::string InstallExtension(Profile* profile, int index) {
   return SyncExtensionHelper::GetInstance()->InstallExtension(
-      profile, CreateFakeExtensionName(index), Extension::TYPE_EXTENSION);
+      profile,
+      CreateFakeExtensionName(index),
+      extensions::Extension::TYPE_EXTENSION);
 }
 
 std::string InstallExtensionForAllProfiles(int index) {
@@ -111,7 +113,7 @@ bool IsIncognitoEnabled(Profile* profile, int index) {
 
 void InstallExtensionsPendingForSync(Profile* profile) {
   SyncExtensionHelper::GetInstance()->InstallExtensionsPendingForSync(
-      profile, Extension::TYPE_EXTENSION);
+      profile, extensions::Extension::TYPE_EXTENSION);
 }
 
 std::string CreateFakeExtensionName(int index) {
diff --git a/chrome/browser/sync/test/integration/sync_app_helper.cc b/chrome/browser/sync/test/integration/sync_app_helper.cc
index efa61c7..e70128d 100644
--- a/chrome/browser/sync/test/integration/sync_app_helper.cc
+++ b/chrome/browser/sync/test/integration/sync_app_helper.cc
@@ -60,7 +60,7 @@ AppStateMap GetAppStates(Profile* profile) {
       extension_service->GenerateInstalledExtensionsSet());
   for (ExtensionSet::const_iterator it = extensions->begin();
        it != extensions->end(); ++it) {
-    if ((*it)->GetSyncType() == Extension::SYNC_TYPE_APP) {
+    if ((*it)->GetSyncType() == extensions::Extension::SYNC_TYPE_APP) {
       const std::string& id = (*it)->id();
       LoadApp(extension_service, id, &(app_state_map[id]));
     }
diff --git a/chrome/browser/sync/test/integration/sync_extension_helper.cc b/chrome/browser/sync/test/integration/sync_extension_helper.cc
index 41db664..f32989a 100644
--- a/chrome/browser/sync/test/integration/sync_extension_helper.cc
+++ b/chrome/browser/sync/test/integration/sync_extension_helper.cc
@@ -20,6 +20,8 @@
 #include "chrome/browser/sync/test/integration/sync_datatype_helper.h"
 #include "testing/gtest/include/gtest/gtest.h"
 
+using extensions::Extension;
+
 SyncExtensionHelper::ExtensionState::ExtensionState()
     : enabled_state(ENABLED), incognito_enabled(false) {}
 
diff --git a/chrome/browser/sync/test/integration/sync_extension_helper.h b/chrome/browser/sync/test/integration/sync_extension_helper.h
index 1e85afe..2b1dc71 100644
--- a/chrome/browser/sync/test/integration/sync_extension_helper.h
+++ b/chrome/browser/sync/test/integration/sync_extension_helper.h
@@ -19,6 +19,10 @@
 class Profile;
 class SyncTest;
 
+namespace extensions {
+class Extension;
+}
+
 class SyncExtensionHelper {
  public:
   // Singleton implementation.
@@ -33,8 +37,9 @@ class SyncExtensionHelper {
 
   // Installs the extension with the given name to |profile|, and returns the
   // extension ID of the new extension.
-  std::string InstallExtension(
-      Profile* profile, const std::string& name, Extension::Type type);
+  std::string InstallExtension(Profile* profile,
+                               const std::string& name,
+                               extensions::Extension::Type type);
 
   // Uninstalls the extension with the given name from |profile|.
   void UninstallExtension(Profile* profile, const std::string& name);
@@ -68,7 +73,8 @@ class SyncExtensionHelper {
 
   // Installs all extensions pending sync in |profile| of the given
   // type.
-  void InstallExtensionsPendingForSync(Profile* profile, Extension::Type type);
+  void InstallExtensionsPendingForSync(Profile* profile,
+                                       extensions::Extension::Type type);
 
   // Returns true iff |profile1| and |profile2| have the same extensions and
   // they are all in the same state.
@@ -87,7 +93,8 @@ class SyncExtensionHelper {
   };
 
   typedef std::map<std::string, ExtensionState> ExtensionStateMap;
-  typedef std::map<std::string, scoped_refptr<Extension> > ExtensionNameMap;
+  typedef std::map<std::string, scoped_refptr<extensions::Extension> >
+      ExtensionNameMap;
   typedef std::map<Profile*, ExtensionNameMap> ProfileExtensionNameMap;
   typedef std::map<std::string, std::string> StringMap;
 
@@ -106,9 +113,9 @@ class SyncExtensionHelper {
   // Returns an extension for the given name in |profile|.  type and
   // index.  Two extensions with the name but different profiles will
   // have the same id.
-  scoped_refptr<Extension> GetExtension(
+  scoped_refptr<extensions::Extension> GetExtension(
       Profile* profile, const std::string& name,
-      Extension::Type type) WARN_UNUSED_RESULT;
+      extensions::Extension::Type type) WARN_UNUSED_RESULT;
 
   ProfileExtensionNameMap profile_extensions_;
   StringMap id_to_name_;
diff --git a/chrome/browser/sync/test/integration/themes_helper.cc b/chrome/browser/sync/test/integration/themes_helper.cc
index d2d9edd..0ff10ce 100644
--- a/chrome/browser/sync/test/integration/themes_helper.cc
+++ b/chrome/browser/sync/test/integration/themes_helper.cc
@@ -60,7 +60,7 @@ bool HasOrWillHaveCustomTheme(Profile* profile, const std::string& id) {
 
 void UseCustomTheme(Profile* profile, int index) {
   SyncExtensionHelper::GetInstance()->InstallExtension(
-      profile, MakeName(index), Extension::TYPE_THEME);
+      profile, MakeName(index), extensions::Extension::TYPE_THEME);
 }
 
 void UseDefaultTheme(Profile* profile) {
diff --git a/chrome/browser/tab_contents/render_view_context_menu.cc b/chrome/browser/tab_contents/render_view_context_menu.cc
index 59d76443..108c062 100644
--- a/chrome/browser/tab_contents/render_view_context_menu.cc
+++ b/chrome/browser/tab_contents/render_view_context_menu.cc
@@ -103,6 +103,7 @@ using content::RenderViewHost;
 using content::SSLStatus;
 using content::UserMetricsAction;
 using content::WebContents;
+using extensions::Extension;
 
 namespace {
 
diff --git a/chrome/browser/tab_contents/render_view_context_menu.h b/chrome/browser/tab_contents/render_view_context_menu.h
index 94a6441..4f6323e 100644
--- a/chrome/browser/tab_contents/render_view_context_menu.h
+++ b/chrome/browser/tab_contents/render_view_context_menu.h
@@ -33,6 +33,10 @@ class RenderViewHost;
 class WebContents;
 }
 
+namespace extensions {
+class Extension;
+}
+
 namespace gfx {
 class Point;
 }
@@ -204,7 +208,7 @@ class RenderViewContextMenu : public ui::SimpleMenuModel::Delegate,
       bool can_cross_incognito);
 
   // Gets the extension (if any) associated with the WebContents that we're in.
-  const Extension* GetExtension() const;
+  const extensions::Extension* GetExtension() const;
   void AppendPlatformAppItems();
   void AppendPopupExtensionItems();
   bool AppendCustomItems();
diff --git a/chrome/browser/task_manager/task_manager.cc b/chrome/browser/task_manager/task_manager.cc
index 8aa2419..395493f 100644
--- a/chrome/browser/task_manager/task_manager.cc
+++ b/chrome/browser/task_manager/task_manager.cc
@@ -486,7 +486,8 @@ TabContentsWrapper* TaskManagerModel::GetResourceTabContents(int index) const {
   return resources_[index]->GetTabContents();
 }
 
-const Extension* TaskManagerModel::GetResourceExtension(int index) const {
+const extensions::Extension* TaskManagerModel::GetResourceExtension(
+    int index) const {
   CHECK_LT(index, ResourceCount());
   return resources_[index]->GetExtension();
 }
diff --git a/chrome/browser/task_manager/task_manager.h b/chrome/browser/task_manager/task_manager.h
index 3e70748..23e582e 100644
--- a/chrome/browser/task_manager/task_manager.h
+++ b/chrome/browser/task_manager/task_manager.h
@@ -21,7 +21,6 @@
 #include "chrome/browser/renderer_host/web_cache_manager.h"
 #include "third_party/WebKit/Source/WebKit/chromium/public/WebCache.h"
 
-class Extension;
 class SkBitmap;
 class TabContentsWrapper;
 class TaskManagerModel;
@@ -29,6 +28,11 @@ class TaskManagerModel;
 namespace base {
 class ProcessMetrics;
 }
+
+namespace extensions {
+class Extension;
+}
+
 namespace net {
 class URLRequest;
 }
@@ -85,7 +89,7 @@ class TaskManager {
 
     // Return extension associated with the resource, or NULL
     // if not applicable.
-    virtual const Extension* GetExtension() const { return NULL; }
+    virtual const extensions::Extension* GetExtension() const { return NULL; }
 
     virtual bool ReportsV8MemoryStats() const { return false; }
     virtual size_t GetV8MemoryAllocated() const { return 0; }
@@ -399,7 +403,7 @@ class TaskManagerModel : public base::RefCountedThreadSafe<TaskManagerModel> {
   TabContentsWrapper* GetResourceTabContents(int index) const;
 
   // Returns Extension of given resource or NULL if not applicable.
-  const Extension* GetResourceExtension(int index) const;
+  const extensions::Extension* GetResourceExtension(int index) const;
 
   void AddResource(TaskManager::Resource* resource);
   void RemoveResource(TaskManager::Resource* resource);
diff --git a/chrome/browser/task_manager/task_manager_browsertest.cc b/chrome/browser/task_manager/task_manager_browsertest.cc
index f049e5d..e19c6fb 100644
--- a/chrome/browser/task_manager/task_manager_browsertest.cc
+++ b/chrome/browser/task_manager/task_manager_browsertest.cc
@@ -254,7 +254,7 @@ IN_PROC_BROWSER_TEST_F(TaskManagerBrowserTest, NoticeAppTabs) {
   ASSERT_TRUE(LoadExtension(
       test_data_dir_.AppendASCII("packaged_app")));
   ExtensionService* service = browser()->profile()->GetExtensionService();
-  const Extension* extension =
+  const extensions::Extension* extension =
       service->GetExtensionById(last_loaded_extension_id_, false);
 
   // Browser and the New Tab Page.
@@ -422,7 +422,7 @@ IN_PROC_BROWSER_TEST_F(TaskManagerBrowserTest, MAYBE_ReloadExtension) {
   EXPECT_TRUE(model()->GetResourceExtension(1) == NULL);
   ASSERT_TRUE(model()->GetResourceExtension(2) != NULL);
 
-  const Extension* extension = model()->GetResourceExtension(2);
+  const extensions::Extension* extension = model()->GetResourceExtension(2);
   ASSERT_TRUE(extension != NULL);
 
   // Reload the extension a few times and make sure our resource count
diff --git a/chrome/browser/task_manager/task_manager_resource_providers.cc b/chrome/browser/task_manager/task_manager_resource_providers.cc
index 96be494..472069e 100644
--- a/chrome/browser/task_manager/task_manager_resource_providers.cc
+++ b/chrome/browser/task_manager/task_manager_resource_providers.cc
@@ -72,6 +72,7 @@
 using content::BrowserChildProcessHostIterator;
 using content::BrowserThread;
 using content::WebContents;
+using extensions::Extension;
 
 namespace {
 
diff --git a/chrome/browser/task_manager/task_manager_resource_providers.h b/chrome/browser/task_manager/task_manager_resource_providers.h
index 721e3ec..612a5ca 100644
--- a/chrome/browser/task_manager/task_manager_resource_providers.h
+++ b/chrome/browser/task_manager/task_manager_resource_providers.h
@@ -21,13 +21,16 @@
 
 class BackgroundContents;
 class BalloonHost;
-class Extension;
 class TabContentsWrapper;
 
 namespace content {
 class RenderViewHost;
 }
 
+namespace extensions {
+class Extension;
+}
+
 // These file contains the resource providers used in the task manager.
 
 // Base class for various types of render process resources that provides common
@@ -112,7 +115,7 @@ class TaskManagerTabContentsResource : public TaskManagerRendererResource {
   virtual string16 GetProfileName() const OVERRIDE;
   virtual SkBitmap GetIcon() const OVERRIDE;
   virtual TabContentsWrapper* GetTabContents() const OVERRIDE;
-  virtual const Extension* GetExtension() const OVERRIDE;
+  virtual const extensions::Extension* GetExtension() const OVERRIDE;
 
  private:
   bool IsPrerendering() const;
@@ -358,7 +361,7 @@ class TaskManagerExtensionProcessResource : public TaskManager::Resource {
   virtual void Inspect() const OVERRIDE;
   virtual bool SupportNetworkUsage() const OVERRIDE;
   virtual void SetSupportNetworkUsage() OVERRIDE;
-  virtual const Extension* GetExtension() const OVERRIDE;
+  virtual const extensions::Extension* GetExtension() const OVERRIDE;
 
   // Returns the pid of the extension process.
   int process_id() const { return pid_; }
diff --git a/chrome/browser/themes/browser_theme_pack.cc b/chrome/browser/themes/browser_theme_pack.cc
index b5f17eb..a62807f 100644
--- a/chrome/browser/themes/browser_theme_pack.cc
+++ b/chrome/browser/themes/browser_theme_pack.cc
@@ -29,6 +29,7 @@
 #include "ui/gfx/skbitmap_operations.h"
 
 using content::BrowserThread;
+using extensions::Extension;
 
 namespace {
 
diff --git a/chrome/browser/themes/browser_theme_pack.h b/chrome/browser/themes/browser_theme_pack.h
index 1a5e648..e582692 100644
--- a/chrome/browser/themes/browser_theme_pack.h
+++ b/chrome/browser/themes/browser_theme_pack.h
@@ -18,15 +18,22 @@
 #include "ui/gfx/color_utils.h"
 
 class FilePath;
-namespace ui {
-class DataPack;
+
+namespace base {
+class DictionaryValue;
+class RefCountedMemory;
+}
+
+namespace extensions {
+class Extensions;
 }
+
 namespace gfx {
 class Image;
 }
-namespace base {
-class DictionaryValue;
-class RefCountedMemory;
+
+namespace ui {
+class DataPack;
 }
 
 // An optimized representation of a theme, backed by a mmapped DataPack.
@@ -53,7 +60,7 @@ class BrowserThemePack : public base::RefCountedThreadSafe<
   // on a separate thread as it takes so long. This can fail and return NULL in
   // the case where the theme has invalid data.
   static scoped_refptr<BrowserThemePack> BuildFromExtension(
-      const Extension* extension);
+      const extensions::Extension* extension);
 
   // Builds the theme pack from a previously performed WriteToDisk(). This
   // operation should be relatively fast, as it should be an mmap() and some
@@ -118,7 +125,7 @@ class BrowserThemePack : public base::RefCountedThreadSafe<
   virtual ~BrowserThemePack();
 
   // Builds a header ready to write to disk.
-  void BuildHeader(const Extension* extension);
+  void BuildHeader(const extensions::Extension* extension);
 
   // Transforms the JSON tint values into their final versions in the |tints_|
   // array.
diff --git a/chrome/browser/themes/browser_theme_pack_unittest.cc b/chrome/browser/themes/browser_theme_pack_unittest.cc
index bcf81ef..008e5c2 100644
--- a/chrome/browser/themes/browser_theme_pack_unittest.cc
+++ b/chrome/browser/themes/browser_theme_pack_unittest.cc
@@ -20,6 +20,7 @@
 #include "ui/gfx/color_utils.h"
 
 using content::BrowserThread;
+using extensions::Extension;
 
 class BrowserThemePackTest : public ::testing::Test {
  public:
diff --git a/chrome/browser/themes/theme_service.cc b/chrome/browser/themes/theme_service.cc
index f9be837..ce26a24 100644
--- a/chrome/browser/themes/theme_service.cc
+++ b/chrome/browser/themes/theme_service.cc
@@ -30,6 +30,7 @@
 
 using content::BrowserThread;
 using content::UserMetricsAction;
+using extensions::Extension;
 using ui::ResourceBundle;
 
 // Strings used in alignment properties.
diff --git a/chrome/browser/themes/theme_service.h b/chrome/browser/themes/theme_service.h
index c5cc1ba..f9c7b30 100644
--- a/chrome/browser/themes/theme_service.h
+++ b/chrome/browser/themes/theme_service.h
@@ -21,7 +21,6 @@
 
 class BrowserThemePack;
 class ThemeServiceTest;
-class Extension;
 class FilePath;
 class Profile;
 
@@ -29,6 +28,10 @@ namespace color_utils {
 struct HSL;
 }
 
+namespace extensions {
+class Extension;
+}
+
 namespace gfx {
 class Image;
 }
@@ -178,7 +181,7 @@ class ThemeService : public base::NonThreadSafe,
 #endif
 
   // Set the current theme to the theme defined in |extension|.
-  virtual void SetTheme(const Extension* extension);
+  virtual void SetTheme(const extensions::Extension* extension);
 
   // Reset the theme to default.
   virtual void UseDefaultTheme();
@@ -281,7 +284,7 @@ class ThemeService : public base::NonThreadSafe,
 
   // Implementation of SetTheme() (and the fallback from LoadThemePrefs() in
   // case we don't have a theme pack).
-  void BuildFromExtension(const Extension* extension);
+  void BuildFromExtension(const extensions::Extension* extension);
 
 #if defined(TOOLKIT_GTK)
   // Loads an image and flips it horizontally if |rtl_enabled| is true.
diff --git a/chrome/browser/themes/theme_service_factory.cc b/chrome/browser/themes/theme_service_factory.cc
index aeefcc8..8d37c3e 100644
--- a/chrome/browser/themes/theme_service_factory.cc
+++ b/chrome/browser/themes/theme_service_factory.cc
@@ -23,7 +23,8 @@ ThemeService* ThemeServiceFactory::GetForProfile(Profile* profile) {
 }
 
 // static
-const Extension* ThemeServiceFactory::GetThemeForProfile(Profile* profile) {
+const extensions::Extension* ThemeServiceFactory::GetThemeForProfile(
+    Profile* profile) {
   std::string id = GetForProfile(profile)->GetThemeID();
   if (id == ThemeService::kDefaultThemeID)
     return NULL;
diff --git a/chrome/browser/themes/theme_service_factory.h b/chrome/browser/themes/theme_service_factory.h
index 9b590b1..2b688ec 100644
--- a/chrome/browser/themes/theme_service_factory.h
+++ b/chrome/browser/themes/theme_service_factory.h
@@ -9,9 +9,12 @@
 #include "base/memory/singleton.h"
 #include "chrome/browser/profiles/profile_keyed_service_factory.h"
 
+class Profile;
 class ThemeService;
+
+namespace extensions {
 class Extension;
-class Profile;
+}
 
 // Singleton that owns all ThemeServices and associates them with
 // Profiles. Listens for the Profile's destruction notification and cleans up
@@ -26,7 +29,7 @@ class ThemeServiceFactory : public ProfileKeyedServiceFactory {
   // Returns the Extension that implements the theme associated with
   // |profile|. Returns NULL if the theme is no longer installed, if there is
   // no installed theme, or the theme was cleared.
-  static const Extension* GetThemeForProfile(Profile* profile);
+  static const extensions::Extension* GetThemeForProfile(Profile* profile);
 
   static ThemeServiceFactory* GetInstance();
 
diff --git a/chrome/browser/ui/app_modal_dialogs/message_box_handler.cc b/chrome/browser/ui/app_modal_dialogs/message_box_handler.cc
index 54f22ad..1f7e2fb 100644
--- a/chrome/browser/ui/app_modal_dialogs/message_box_handler.cc
+++ b/chrome/browser/ui/app_modal_dialogs/message_box_handler.cc
@@ -227,7 +227,7 @@ string16 ChromeJavaScriptDialogCreator::GetTitle(const GURL& origin_url,
 
   // If the URL is a chrome extension one, return the extension name.
   if (extension_host_) {
-    const Extension* extension = extension_host_->
+    const extensions::Extension* extension = extension_host_->
       profile()->GetExtensionService()->extensions()->
       GetExtensionOrAppByURL(ExtensionURLInfo(origin_url));
     if (extension) {
diff --git a/chrome/browser/ui/browser.cc b/chrome/browser/ui/browser.cc
index f001aa5..987af6c 100644
--- a/chrome/browser/ui/browser.cc
+++ b/chrome/browser/ui/browser.cc
@@ -226,6 +226,7 @@ using content::SiteInstance;
 using content::SSLStatus;
 using content::UserMetricsAction;
 using content::WebContents;
+using extensions::Extension;
 
 ///////////////////////////////////////////////////////////////////////////////
 
@@ -4112,10 +4113,11 @@ void Browser::Observe(int type,
 
       // Close any tabs from the unloaded extension, unless it's terminated,
       // in which case let the sad tabs remain.
-      if (content::Details<UnloadedExtensionInfo>(details)->reason !=
-          extension_misc::UNLOAD_REASON_TERMINATE) {
+      if (content::Details<extensions::UnloadedExtensionInfo>(
+            details)->reason != extension_misc::UNLOAD_REASON_TERMINATE) {
         const Extension* extension =
-            content::Details<UnloadedExtensionInfo>(details)->extension;
+            content::Details<extensions::UnloadedExtensionInfo>(
+                details)->extension;
         for (int i = tab_strip_model_->count() - 1; i >= 0; --i) {
           WebContents* tc =
               tab_strip_model_->GetTabContentsAt(i)->web_contents();
diff --git a/chrome/browser/ui/browser.h b/chrome/browser/ui/browser.h
index 5dc3dce..048de21 100644
--- a/chrome/browser/ui/browser.h
+++ b/chrome/browser/ui/browser.h
@@ -56,7 +56,6 @@ class BrowserSyncedWindowDelegate;
 class BrowserToolbarModelDelegate;
 class BrowserTabRestoreServiceDelegate;
 class BrowserWindow;
-class Extension;
 class ExtensionWindowController;
 class FindBarController;
 class FullscreenController;
@@ -76,6 +75,10 @@ class NavigationController;
 class SessionStorageNamespace;
 }
 
+namespace extensions {
+class Extension;
+}
+
 namespace gfx {
 class Point;
 }
@@ -290,7 +293,7 @@ class Browser : public TabStripModelDelegate,
   // |override_url| is used in place of the app launch url.
   static content::WebContents* OpenApplication(
       Profile* profile,
-      const Extension* extension,
+      const extensions::Extension* extension,
       extension_misc::LaunchContainer container,
       const GURL& override_url,
       WindowOpenDisposition disposition);
@@ -299,7 +302,7 @@ class Browser : public TabStripModelDelegate,
   // Opens |url| in a new application panel window for the specified url.
   static content::WebContents* OpenApplicationPanel(
       Profile* profile,
-      const Extension* extension,
+      const extensions::Extension* extension,
       const GURL& url);
 #endif
 
@@ -312,7 +315,7 @@ class Browser : public TabStripModelDelegate,
   // returned tab.
   static content::WebContents* OpenApplicationWindow(
       Profile* profile,
-      const Extension* extension,
+      const extensions::Extension* extension,
       extension_misc::LaunchContainer container,
       const GURL& url,
       Browser** app_browser);
@@ -332,7 +335,7 @@ class Browser : public TabStripModelDelegate,
   // non-empty, |override_url| is used in place of the app launch url.
   static content::WebContents* OpenApplicationTab(
       Profile* profile,
-      const Extension* extension,
+      const extensions::Extension* extension,
       const GURL& override_url,
       WindowOpenDisposition disposition);
 
diff --git a/chrome/browser/ui/browser_browsertest.cc b/chrome/browser/ui/browser_browsertest.cc
index 02a51c3..26e7ece 100644
--- a/chrome/browser/ui/browser_browsertest.cc
+++ b/chrome/browser/ui/browser_browsertest.cc
@@ -76,6 +76,7 @@ using content::OpenURLParams;
 using content::Referrer;
 using content::WebContents;
 using content::WebContentsObserver;
+using extensions::Extension;
 
 namespace {
 
diff --git a/chrome/browser/ui/browser_dialogs.h b/chrome/browser/ui/browser_dialogs.h
index a885730..16174fa 100644
--- a/chrome/browser/ui/browser_dialogs.h
+++ b/chrome/browser/ui/browser_dialogs.h
@@ -10,7 +10,6 @@
 #include "ui/gfx/native_widget_types.h"
 
 class Browser;
-class Extension;
 class Profile;
 class SkBitmap;
 class TabContentsWrapper;
@@ -22,6 +21,10 @@ namespace content {
 class WebContents;
 }
 
+namespace extensions {
+class Extension;
+}
+
 namespace browser {
 
 #if defined(IPC_MESSAGE_LOG_ENABLED)
@@ -54,7 +57,7 @@ void ShowCollectedCookiesDialog(gfx::NativeWindow parent_window,
 // the extension has loaded. |extension| is the installed extension. |browser|
 // is the browser window which will host the bubble. |icon| is the install
 // icon of the extension.
-void ShowExtensionInstalledBubble(const Extension* extension,
+void ShowExtensionInstalledBubble(const extensions::Extension* extension,
                                   Browser* browser,
                                   const SkBitmap& icon,
                                   Profile* profile);
diff --git a/chrome/browser/ui/browser_window.h b/chrome/browser/ui/browser_window.h
index 12aa098..508249a 100644
--- a/chrome/browser/ui/browser_window.h
+++ b/chrome/browser/ui/browser_window.h
@@ -35,12 +35,15 @@ struct NativeWebKeyboardEvent;
 struct SSLStatus;
 }
 
+namespace extensions {
+class Extension;
+}
+
 namespace gfx {
 class Rect;
 class Size;
 }
 
-class Extension;
 
 enum DevToolsDockSide {
   DEVTOOLS_DOCK_SIDE_BOTTOM = 0,
@@ -293,7 +296,8 @@ class BrowserWindow : public BaseWindow {
 
   // Shows the create chrome app shortcut dialog box.
   virtual void ShowCreateChromeAppShortcutsDialog(Profile* profile,
-                                                  const Extension* app) = 0;
+      const extensions::Extension* app) = 0;
+
 
   // Clipboard commands applied to the whole browser window.
   virtual void Cut() = 0;
diff --git a/chrome/browser/ui/cocoa/browser_window_cocoa.h b/chrome/browser/ui/cocoa/browser_window_cocoa.h
index 43c52e6..d7640f4 100644
--- a/chrome/browser/ui/cocoa/browser_window_cocoa.h
+++ b/chrome/browser/ui/cocoa/browser_window_cocoa.h
@@ -21,6 +21,10 @@ class Browser;
 @class NSMenu;
 @class NSWindow;
 
+namespace extensions {
+class Extension;
+}
+
 // An implementation of BrowserWindow for Cocoa. Bridges between C++ and
 // the Cocoa NSWindow. Cross-platform code will interact with this object when
 // it needs to manipulate the window.
@@ -123,7 +127,7 @@ class BrowserWindowCocoa : public BrowserWindow,
       TabContentsWrapper* tab_contents) OVERRIDE;
   virtual void ShowCreateChromeAppShortcutsDialog(
       Profile* profile,
-      const Extension* app) OVERRIDE;
+      const extensions::Extension* app) OVERRIDE;
   virtual void Cut() OVERRIDE;
   virtual void Copy() OVERRIDE;
   virtual void Paste() OVERRIDE;
diff --git a/chrome/browser/ui/cocoa/browser_window_cocoa.mm b/chrome/browser/ui/cocoa/browser_window_cocoa.mm
index 4e01a62..c0bf3ce 100644
--- a/chrome/browser/ui/cocoa/browser_window_cocoa.mm
+++ b/chrome/browser/ui/cocoa/browser_window_cocoa.mm
@@ -547,7 +547,7 @@ void BrowserWindowCocoa::ShowCreateWebAppShortcutsDialog(
 }
 
 void BrowserWindowCocoa::ShowCreateChromeAppShortcutsDialog(
-    Profile* profile, const Extension* app) {
+    Profile* profile, const extensions::Extension* app) {
   NOTIMPLEMENTED();
 }
 
diff --git a/chrome/browser/ui/cocoa/extensions/browser_action_button.h b/chrome/browser/ui/cocoa/extensions/browser_action_button.h
index e8bad88..1b4eceb 100644
--- a/chrome/browser/ui/cocoa/extensions/browser_action_button.h
+++ b/chrome/browser/ui/cocoa/extensions/browser_action_button.h
@@ -12,11 +12,14 @@
 #include "base/memory/scoped_ptr.h"
 #import "chrome/browser/ui/cocoa/gradient_button_cell.h"
 
-class Extension;
 class ExtensionAction;
 class ExtensionImageTrackerBridge;
 class Profile;
 
+namespace extensions {
+class Extension;
+}
+
 // Fired when the Browser Action's state has changed. Usually the image needs to
 // be updated.
 extern NSString* const kBrowserActionButtonUpdatedNotification;
@@ -42,7 +45,7 @@ extern NSString* const kBrowserActionButtonDragEndNotification;
   scoped_nsobject<NSViewAnimation> moveAnimation_;
 
   // The extension for this button. Weak.
-  const Extension* extension_;
+  const extensions::Extension* extension_;
 
   // The ID of the active tab.
   int tabId_;
@@ -57,7 +60,7 @@ extern NSString* const kBrowserActionButtonDragEndNotification;
 }
 
 - (id)initWithFrame:(NSRect)frame
-          extension:(const Extension*)extension
+          extension:(const extensions::Extension*)extension
             profile:(Profile*)profile
               tabId:(int)tabId;
 
@@ -76,7 +79,7 @@ extern NSString* const kBrowserActionButtonDragEndNotification;
 - (NSImage*)compositedImage;
 
 @property(readonly, nonatomic) BOOL isBeingDragged;
-@property(readonly, nonatomic) const Extension* extension;
+@property(readonly, nonatomic) const extensions::Extension* extension;
 @property(readwrite, nonatomic) int tabId;
 
 @end
diff --git a/chrome/browser/ui/cocoa/extensions/browser_action_button.mm b/chrome/browser/ui/cocoa/extensions/browser_action_button.mm
index 3c5617d..bdd25c7 100644
--- a/chrome/browser/ui/cocoa/extensions/browser_action_button.mm
+++ b/chrome/browser/ui/cocoa/extensions/browser_action_button.mm
@@ -29,6 +29,8 @@
 #include "ui/gfx/scoped_ns_graphics_context_save_gstate_mac.h"
 #include "ui/gfx/size.h"
 
+using extensions::Extension;
+
 NSString* const kBrowserActionButtonUpdatedNotification =
     @"BrowserActionButtonUpdatedNotification";
 
diff --git a/chrome/browser/ui/cocoa/extensions/browser_actions_controller.h b/chrome/browser/ui/cocoa/extensions/browser_actions_controller.h
index 02a26d9..59001cd 100644
--- a/chrome/browser/ui/cocoa/extensions/browser_actions_controller.h
+++ b/chrome/browser/ui/cocoa/extensions/browser_actions_controller.h
@@ -14,7 +14,6 @@
 class Browser;
 @class BrowserActionButton;
 @class BrowserActionsContainerView;
-class Extension;
 @class ExtensionPopupController;
 class ExtensionToolbarModel;
 class ExtensionServiceObserverBridge;
@@ -22,6 +21,10 @@ class ExtensionServiceObserverBridge;
 class PrefService;
 class Profile;
 
+namespace extensions {
+class Extension;
+}
+
 // Sent when the visibility of the Browser Actions changes.
 extern NSString* const kBrowserActionVisibilityChangedNotification;
 
@@ -88,7 +91,8 @@ extern NSString* const kBrowserActionVisibilityChangedNotification;
 - (void)resizeContainerAndAnimate:(BOOL)animate;
 
 // Returns the NSView for the action button associated with an extension.
-- (NSView*)browserActionViewForExtension:(const Extension*)extension;
+- (NSView*)browserActionViewForExtension:(
+    const extensions::Extension*)extension;
 
 // Returns the saved width determined by the number of shown Browser Actions
 // preference property. If no preference is found, then the width for the
@@ -98,7 +102,7 @@ extern NSString* const kBrowserActionVisibilityChangedNotification;
 // Returns where the popup arrow should point to for a given Browser Action. If
 // it is passed an extension that is not a Browser Action, then it will return
 // NSZeroPoint.
-- (NSPoint)popupPointForBrowserAction:(const Extension*)extension;
+- (NSPoint)popupPointForBrowserAction:(const extensions::Extension*)extension;
 
 // Returns whether the chevron button is currently hidden or in the process of
 // being hidden (fading out). Will return NO if it is not hidden or is in the
diff --git a/chrome/browser/ui/cocoa/extensions/browser_actions_controller.mm b/chrome/browser/ui/cocoa/extensions/browser_actions_controller.mm
index 046f2e5..a946a22 100644
--- a/chrome/browser/ui/cocoa/extensions/browser_actions_controller.mm
+++ b/chrome/browser/ui/cocoa/extensions/browser_actions_controller.mm
@@ -34,6 +34,9 @@
 #import "third_party/GTM/AppKit/GTMNSAnimation+Duration.h"
 #include "ui/gfx/mac/nsimage_cache.h"
 
+using extensions::Extension;
+using extensions::ExtensionList;
+
 NSString* const kBrowserActionVisibilityChangedNotification =
     @"BrowserActionVisibilityChangedNotification";
 
diff --git a/chrome/browser/ui/cocoa/extensions/extension_action_context_menu.h b/chrome/browser/ui/cocoa/extensions/extension_action_context_menu.h
index 8904fa8..addb655 100644
--- a/chrome/browser/ui/cocoa/extensions/extension_action_context_menu.h
+++ b/chrome/browser/ui/cocoa/extensions/extension_action_context_menu.h
@@ -12,10 +12,13 @@
 #include "base/memory/scoped_ptr.h"
 
 class AsyncUninstaller;
-class Extension;
 class ExtensionAction;
 class Profile;
 
+namespace extensions {
+class Extension;
+}
+
 namespace extension_action_context_menu {
 
 }  // namespace extension_action_context_menu
@@ -24,7 +27,7 @@ namespace extension_action_context_menu {
 @interface ExtensionActionContextMenu : NSMenu {
  @private
   // The extension that this menu belongs to. Weak.
-  const Extension* extension_;
+  const extensions::Extension* extension_;
 
   // The extension action this menu belongs to. Weak.
   ExtensionAction* action_;
@@ -38,7 +41,7 @@ namespace extension_action_context_menu {
 }
 
 // Initializes and returns a context menu for the given extension and profile.
-- (id)initWithExtension:(const Extension*)extension
+- (id)initWithExtension:(const extensions::Extension*)extension
                 profile:(Profile*)profile
         extensionAction:(ExtensionAction*)action;
 
diff --git a/chrome/browser/ui/cocoa/extensions/extension_action_context_menu.mm b/chrome/browser/ui/cocoa/extensions/extension_action_context_menu.mm
index 1b63043a..401481c 100644
--- a/chrome/browser/ui/cocoa/extensions/extension_action_context_menu.mm
+++ b/chrome/browser/ui/cocoa/extensions/extension_action_context_menu.mm
@@ -38,6 +38,7 @@
 using content::OpenURLParams;
 using content::Referrer;
 using content::WebContents;
+using extensions::Extension;
 
 // A class that loads the extension icon on the I/O thread before showing the
 // confirmation dialog to uninstall the given extension.
diff --git a/chrome/browser/ui/cocoa/extensions/extension_install_dialog_controller.h b/chrome/browser/ui/cocoa/extensions/extension_install_dialog_controller.h
index 6a58c94..9cab254 100644
--- a/chrome/browser/ui/cocoa/extensions/extension_install_dialog_controller.h
+++ b/chrome/browser/ui/cocoa/extensions/extension_install_dialog_controller.h
@@ -15,7 +15,6 @@
 #include "chrome/browser/extensions/extension_install_ui.h"
 #include "third_party/skia/include/core/SkBitmap.h"
 
-class Extension;
 class Profile;
 
 // Displays the extension or bundle install prompt, and notifies the
diff --git a/chrome/browser/ui/cocoa/extensions/extension_install_dialog_controller_unittest.mm b/chrome/browser/ui/cocoa/extensions/extension_install_dialog_controller_unittest.mm
index 2daa7f1..2e9b7d6 100644
--- a/chrome/browser/ui/cocoa/extensions/extension_install_dialog_controller_unittest.mm
+++ b/chrome/browser/ui/cocoa/extensions/extension_install_dialog_controller_unittest.mm
@@ -25,6 +25,7 @@
 #include "ui/gfx/image/image.h"
 #include "webkit/glue/image_decoder.h"
 
+using extensions::Extension;
 
 // Base class for our tests.
 class ExtensionInstallDialogControllerTest : public CocoaProfileTest {
diff --git a/chrome/browser/ui/cocoa/extensions/extension_installed_bubble_bridge.mm b/chrome/browser/ui/cocoa/extensions/extension_installed_bubble_bridge.mm
index 133beda..678f83c 100644
--- a/chrome/browser/ui/cocoa/extensions/extension_installed_bubble_bridge.mm
+++ b/chrome/browser/ui/cocoa/extensions/extension_installed_bubble_bridge.mm
@@ -28,7 +28,7 @@ using extensions::BundleInstaller;
 // When an extension is installed on Mac with neither browser action nor
 // page action icons, show an infobar instead of a popup bubble.
 static void ShowGenericExtensionInstalledInfoBar(
-    const Extension* new_extension,
+    const extensions::Extension* new_extension,
     const SkBitmap& icon,
     Profile* profile) {
   Browser* browser = browser::FindLastActiveWithProfile(profile);
@@ -55,7 +55,7 @@ static void ShowGenericExtensionInstalledInfoBar(
 namespace browser {
 
 void ShowExtensionInstalledBubble(
-    const Extension* extension,
+    const extensions::Extension* extension,
     Browser* browser,
     const SkBitmap& icon,
     Profile* profile) {
diff --git a/chrome/browser/ui/cocoa/extensions/extension_installed_bubble_controller.h b/chrome/browser/ui/cocoa/extensions/extension_installed_bubble_controller.h
index b31d6c6..a4a76b9 100644
--- a/chrome/browser/ui/cocoa/extensions/extension_installed_bubble_controller.h
+++ b/chrome/browser/ui/cocoa/extensions/extension_installed_bubble_controller.h
@@ -15,13 +15,13 @@
 #include "third_party/skia/include/core/SkBitmap.h"
 
 class Browser;
-class Extension;
 class ExtensionLoadedNotificationObserver;
 @class HoverCloseButton;
 @class InfoBubbleView;
 
 namespace extensions {
 class BundleInstaller;
+class Extension;
 }
 
 namespace extension_installed_bubble {
@@ -52,7 +52,7 @@ typedef enum {
 // future.
 @interface ExtensionInstalledBubbleController : BaseBubbleController {
  @private
-  const Extension* extension_;  // weak
+  const extensions::Extension* extension_;  // weak
   const extensions::BundleInstaller* bundle_;  // weak
   Browser* browser_;  // weak
   scoped_nsobject<NSImage> icon_;
@@ -83,14 +83,14 @@ typedef enum {
   IBOutlet NSTextField* failedItemsMsg_;
 }
 
-@property(nonatomic, readonly) const Extension* extension;
+@property(nonatomic, readonly) const extensions::Extension* extension;
 @property(nonatomic, readonly) const extensions::BundleInstaller* bundle;
 @property(nonatomic) BOOL pageActionRemoved;
 
 // Initialize the window, and then create observers to wait for the extension
 // to complete loading, or the browser window to close.
 - (id)initWithParentWindow:(NSWindow*)parentWindow
-                 extension:(const Extension*)extension
+                 extension:(const extensions::Extension*)extension
                     bundle:(const extensions::BundleInstaller*)bundle
                    browser:(Browser*)browser
                       icon:(SkBitmap)icon;
diff --git a/chrome/browser/ui/cocoa/extensions/extension_installed_bubble_controller.mm b/chrome/browser/ui/cocoa/extensions/extension_installed_bubble_controller.mm
index 9d4317e..1869dbf 100644
--- a/chrome/browser/ui/cocoa/extensions/extension_installed_bubble_controller.mm
+++ b/chrome/browser/ui/cocoa/extensions/extension_installed_bubble_controller.mm
@@ -33,6 +33,7 @@
 
 using content::BrowserThread;
 using extensions::BundleInstaller;
+using extensions::Extension;
 
 // C++ class that receives EXTENSION_LOADED notifications and proxies them back
 // to |controller|.
diff --git a/chrome/browser/ui/cocoa/extensions/extension_installed_bubble_controller_unittest.mm b/chrome/browser/ui/cocoa/extensions/extension_installed_bubble_controller_unittest.mm
index aa36932..a26eaa0 100644
--- a/chrome/browser/ui/cocoa/extensions/extension_installed_bubble_controller_unittest.mm
+++ b/chrome/browser/ui/cocoa/extensions/extension_installed_bubble_controller_unittest.mm
@@ -21,6 +21,8 @@
 #import "third_party/ocmock/OCMock/OCMock.h"
 #include "webkit/glue/image_decoder.h"
 
+using extensions::Extension;
+
 // ExtensionInstalledBubbleController with removePageActionPreview overridden
 // to a no-op, because pageActions are not yet hooked up in the test browser.
 @interface ExtensionInstalledBubbleControllerForTest :
diff --git a/chrome/browser/ui/cocoa/extensions/shell_window_cocoa.h b/chrome/browser/ui/cocoa/extensions/shell_window_cocoa.h
index b5020ec..5dfd030 100644
--- a/chrome/browser/ui/cocoa/extensions/shell_window_cocoa.h
+++ b/chrome/browser/ui/cocoa/extensions/shell_window_cocoa.h
@@ -31,7 +31,7 @@ class ShellWindowCocoa;
 class ShellWindowCocoa : public ShellWindow {
  public:
   ShellWindowCocoa(Profile* profile,
-                   const Extension* extension,
+                   const extensions::Extension* extension,
                    const GURL& url);
 
   // BaseWindow implementation.
diff --git a/chrome/browser/ui/cocoa/extensions/shell_window_cocoa.mm b/chrome/browser/ui/cocoa/extensions/shell_window_cocoa.mm
index 01e41fb..03ec1fe 100644
--- a/chrome/browser/ui/cocoa/extensions/shell_window_cocoa.mm
+++ b/chrome/browser/ui/cocoa/extensions/shell_window_cocoa.mm
@@ -25,7 +25,7 @@
 @end
 
 ShellWindowCocoa::ShellWindowCocoa(Profile* profile,
-                                   const Extension* extension,
+                                   const extensions::Extension* extension,
                                    const GURL& url)
     : ShellWindow(profile, extension, url),
       attention_request_id_(0) {
@@ -170,7 +170,7 @@ NSWindow* ShellWindowCocoa::window() const {
 
 // static
 ShellWindow* ShellWindow::CreateImpl(Profile* profile,
-                                     const Extension* extension,
+                                     const extensions::Extension* extension,
                                      const GURL& url) {
   return new ShellWindowCocoa(profile, extension, url);
 }
diff --git a/chrome/browser/ui/cocoa/infobars/extension_infobar_controller.mm b/chrome/browser/ui/cocoa/infobars/extension_infobar_controller.mm
index cff2141..6bae992 100644
--- a/chrome/browser/ui/cocoa/infobars/extension_infobar_controller.mm
+++ b/chrome/browser/ui/cocoa/infobars/extension_infobar_controller.mm
@@ -69,7 +69,8 @@ class InfobarBridge : public ExtensionInfoBarDelegate::DelegateObserver,
 
   // Load the Extension's icon image.
   void LoadIcon() {
-    const Extension* extension = delegate_->extension_host()->extension();
+    const extensions::Extension* extension = delegate_->extension_host()->
+        extension();
     ExtensionResource icon_resource =
         extension->GetIconResource(ExtensionIconSet::EXTENSION_ICON_BITTY,
                                    ExtensionIconSet::MATCH_EXACTLY);
diff --git a/chrome/browser/ui/cocoa/location_bar/page_action_decoration.mm b/chrome/browser/ui/cocoa/location_bar/page_action_decoration.mm
index 29a1bcf..aa7976c 100644
--- a/chrome/browser/ui/cocoa/location_bar/page_action_decoration.mm
+++ b/chrome/browser/ui/cocoa/location_bar/page_action_decoration.mm
@@ -22,6 +22,7 @@
 #include "skia/ext/skia_utils_mac.h"
 
 using content::WebContents;
+using extensions::Extension;
 
 namespace {
 
diff --git a/chrome/browser/ui/extensions/shell_window.cc b/chrome/browser/ui/extensions/shell_window.cc
index ff7881d..701e97c 100644
--- a/chrome/browser/ui/extensions/shell_window.cc
+++ b/chrome/browser/ui/extensions/shell_window.cc
@@ -84,14 +84,14 @@ void ShellWindowController::SetFullscreenMode(bool is_fullscreen,
 }  // namespace internal
 
 ShellWindow* ShellWindow::Create(Profile* profile,
-                                 const Extension* extension,
+                                 const extensions::Extension* extension,
                                  const GURL& url) {
   // This object will delete itself when the window is closed.
   return ShellWindow::CreateImpl(profile, extension, url);
 }
 
 ShellWindow::ShellWindow(Profile* profile,
-                         const Extension* extension,
+                         const extensions::Extension* extension,
                          const GURL& url)
     : profile_(profile),
       extension_(extension),
@@ -180,8 +180,9 @@ void ShellWindow::Observe(int type,
                           const content::NotificationDetails& details) {
   switch (type) {
     case chrome::NOTIFICATION_EXTENSION_UNLOADED: {
-      const Extension* unloaded_extension =
-          content::Details<UnloadedExtensionInfo>(details)->extension;
+      const extensions::Extension* unloaded_extension =
+          content::Details<extensions::UnloadedExtensionInfo>(
+              details)->extension;
       if (extension_ == unloaded_extension)
         Close();
       break;
diff --git a/chrome/browser/ui/extensions/shell_window.h b/chrome/browser/ui/extensions/shell_window.h
index cd42822..386f431 100644
--- a/chrome/browser/ui/extensions/shell_window.h
+++ b/chrome/browser/ui/extensions/shell_window.h
@@ -15,7 +15,6 @@
 #include "content/public/browser/web_contents_delegate.h"
 #include "content/public/browser/web_contents_observer.h"
 
-class Extension;
 class ExtensionWindowController;
 class GURL;
 class Profile;
@@ -25,6 +24,10 @@ namespace content {
 class WebContents;
 }
 
+namespace extensions {
+class Extension;
+}
+
 // ShellWindow is the type of window used by platform apps. Shell windows
 // have a WebContents but none of the chrome of normal browser windows.
 class ShellWindow : public content::NotificationObserver,
@@ -34,7 +37,7 @@ class ShellWindow : public content::NotificationObserver,
                     public BaseWindow {
  public:
   static ShellWindow* Create(Profile* profile,
-                             const Extension* extension,
+                             const extensions::Extension* extension,
                              const GURL& url);
 
   const SessionID& session_id() const { return session_id_; }
@@ -49,11 +52,11 @@ class ShellWindow : public content::NotificationObserver,
   static const int kDefaultHeight = 384;
 
   ShellWindow(Profile* profile,
-              const Extension* extension,
+              const extensions::Extension* extension,
               const GURL& url);
   virtual ~ShellWindow();
 
-  const Extension* extension() const { return extension_; }
+  const extensions::Extension* extension() const { return extension_; }
   content::WebContents* web_contents() const { return web_contents_; }
 
  private:
@@ -63,7 +66,7 @@ class ShellWindow : public content::NotificationObserver,
   // Instantiates a platform-specific ShellWindow subclass (one implementation
   // per platform). Public users of ShellWindow should use ShellWindow::Create.
   static ShellWindow* CreateImpl(Profile* profile,
-                                 const Extension* extension,
+                                 const extensions::Extension* extension,
                                  const GURL& url);
 
   // content::WebContentsObserver implementation.
@@ -92,7 +95,8 @@ class ShellWindow : public content::NotificationObserver,
   void OnRequest(const ExtensionHostMsg_Request_Params& params);
 
   Profile* profile_;  // weak pointer - owned by ProfileManager.
-  const Extension* extension_;  // weak pointer - owned by ExtensionService.
+  // weak pointer - owned by ExtensionService.
+  const extensions::Extension* extension_;
 
   const SessionID session_id_;
   scoped_ptr<TabContentsWrapper> contents_wrapper_;
diff --git a/chrome/browser/ui/fullscreen_exit_bubble_type.cc b/chrome/browser/ui/fullscreen_exit_bubble_type.cc
index 6b27e8e..c5a8565 100644
--- a/chrome/browser/ui/fullscreen_exit_bubble_type.cc
+++ b/chrome/browser/ui/fullscreen_exit_bubble_type.cc
@@ -21,7 +21,7 @@ string16 GetLabelTextForType(FullscreenExitBubbleType type,
   if (extension_service) {
     const ExtensionSet* extensions = extension_service->extensions();
     DCHECK(extensions);
-    const Extension* extension =
+    const extensions::Extension* extension =
         extensions->GetExtensionOrAppByURL(ExtensionURLInfo(url));
     if (extension) {
       host = UTF8ToUTF16(extension->name());
diff --git a/chrome/browser/ui/gtk/browser_actions_toolbar_gtk.cc b/chrome/browser/ui/gtk/browser_actions_toolbar_gtk.cc
index 98337fb..cf1cbef 100644
--- a/chrome/browser/ui/gtk/browser_actions_toolbar_gtk.cc
+++ b/chrome/browser/ui/gtk/browser_actions_toolbar_gtk.cc
@@ -49,6 +49,8 @@
 #include "ui/gfx/gtk_util.h"
 #include "ui/gfx/image/image.h"
 
+using extensions::Extension;
+
 namespace {
 
 // The width of the browser action buttons.
@@ -609,7 +611,7 @@ void BrowserActionsToolbarGtk::CreateAllButtons() {
   extension_button_map_.clear();
 
   int i = 0;
-  for (ExtensionList::iterator iter = model_->begin();
+  for (extensions::ExtensionList::iterator iter = model_->begin();
        iter != model_->end(); ++iter) {
     CreateButtonForExtension(*iter, i++);
   }
diff --git a/chrome/browser/ui/gtk/browser_actions_toolbar_gtk.h b/chrome/browser/ui/gtk/browser_actions_toolbar_gtk.h
index 2aa9185..58b3660 100644
--- a/chrome/browser/ui/gtk/browser_actions_toolbar_gtk.h
+++ b/chrome/browser/ui/gtk/browser_actions_toolbar_gtk.h
@@ -27,10 +27,13 @@
 
 class Browser;
 class BrowserActionButton;
-class Extension;
 class GtkThemeService;
 class Profile;
 
+namespace extensions {
+class Extension;
+}
+
 typedef struct _GdkDragContext GdkDragContext;
 typedef struct _GtkWidget GtkWidget;
 
@@ -49,7 +52,7 @@ class BrowserActionsToolbarGtk : public ExtensionToolbarModel::Observer,
   // Returns the widget in use by the BrowserActionButton corresponding to
   // |extension|. Used in positioning the ExtensionInstalledBubble for
   // BrowserActions.
-  GtkWidget* GetBrowserActionWidget(const Extension* extension);
+  GtkWidget* GetBrowserActionWidget(const extensions::Extension* extension);
 
   int button_count() { return extension_button_map_.size(); }
 
@@ -87,10 +90,11 @@ class BrowserActionsToolbarGtk : public ExtensionToolbarModel::Observer,
 
   // Create the UI for a single browser action. This will stick the button
   // at the end of the toolbar.
-  void CreateButtonForExtension(const Extension* extension, int index);
+  void CreateButtonForExtension(const extensions::Extension* extension,
+                                int index);
 
   // Delete resources associated with UI for a browser action.
-  void RemoveButtonForExtension(const Extension* extension);
+  void RemoveButtonForExtension(const extensions::Extension* extension);
 
   // Change the visibility of widget() based on whether we have any buttons
   // to show.
@@ -106,13 +110,14 @@ class BrowserActionsToolbarGtk : public ExtensionToolbarModel::Observer,
   // Returns true if this extension should be shown in this toolbar. This can
   // return false if we are in an incognito window and the extension is disabled
   // for incognito.
-  bool ShouldDisplayBrowserAction(const Extension* extension);
+  bool ShouldDisplayBrowserAction(const extensions::Extension* extension);
 
   // ExtensionToolbarModel::Observer implementation.
-  virtual void BrowserActionAdded(const Extension* extension,
+  virtual void BrowserActionAdded(const extensions::Extension* extension,
                                   int index) OVERRIDE;
-  virtual void BrowserActionRemoved(const Extension* extension) OVERRIDE;
-  virtual void BrowserActionMoved(const Extension* extension,
+  virtual void BrowserActionRemoved(
+      const extensions::Extension* extension) OVERRIDE;
+  virtual void BrowserActionMoved(const extensions::Extension* extension,
                                   int index) OVERRIDE;
   virtual void ModelLoaded() OVERRIDE;
 
diff --git a/chrome/browser/ui/gtk/browser_window_gtk.cc b/chrome/browser/ui/gtk/browser_window_gtk.cc
index 7ede5fb..85ba20e 100644
--- a/chrome/browser/ui/gtk/browser_window_gtk.cc
+++ b/chrome/browser/ui/gtk/browser_window_gtk.cc
@@ -1224,7 +1224,7 @@ void BrowserWindowGtk::ShowCreateWebAppShortcutsDialog(
 }
 
 void BrowserWindowGtk::ShowCreateChromeAppShortcutsDialog(
-    Profile* profile, const Extension* app) {
+    Profile* profile, const extensions::Extension* app) {
   CreateChromeApplicationShortcutsDialogGtk::Show(window_, profile, app);
 }
 
diff --git a/chrome/browser/ui/gtk/browser_window_gtk.h b/chrome/browser/ui/gtk/browser_window_gtk.h
index 4b79cc7..5924cbe 100644
--- a/chrome/browser/ui/gtk/browser_window_gtk.h
+++ b/chrome/browser/ui/gtk/browser_window_gtk.h
@@ -40,6 +40,10 @@ class StatusBubbleGtk;
 class TabContentsContainerGtk;
 class TabStripGtk;
 
+namespace extensions {
+class Extension;
+}
+
 // An implementation of BrowserWindow for GTK.
 // Cross-platform code will interact with this object when
 // it needs to manipulate the window.
@@ -153,7 +157,7 @@ class BrowserWindowGtk : public BrowserWindow,
       TabContentsWrapper* tab_contents) OVERRIDE;
   virtual void ShowCreateChromeAppShortcutsDialog(
       Profile* profile,
-      const Extension* app) OVERRIDE;
+      const extensions::Extension* app) OVERRIDE;
   virtual void Cut() OVERRIDE;
   virtual void Copy() OVERRIDE;
   virtual void Paste() OVERRIDE;
diff --git a/chrome/browser/ui/gtk/create_application_shortcuts_dialog_gtk.cc b/chrome/browser/ui/gtk/create_application_shortcuts_dialog_gtk.cc
index 1ae913b..c73ed67 100644
--- a/chrome/browser/ui/gtk/create_application_shortcuts_dialog_gtk.cc
+++ b/chrome/browser/ui/gtk/create_application_shortcuts_dialog_gtk.cc
@@ -32,6 +32,7 @@
 #include "ui/gfx/gtk_util.h"
 
 using content::BrowserThread;
+using extensions::Extension;
 
 namespace {
 
diff --git a/chrome/browser/ui/gtk/create_application_shortcuts_dialog_gtk.h b/chrome/browser/ui/gtk/create_application_shortcuts_dialog_gtk.h
index 01de16c..6253f8b 100644
--- a/chrome/browser/ui/gtk/create_application_shortcuts_dialog_gtk.h
+++ b/chrome/browser/ui/gtk/create_application_shortcuts_dialog_gtk.h
@@ -22,10 +22,13 @@ typedef struct _GdkPixbuf GdkPixbuf;
 typedef struct _GtkWidget GtkWidget;
 typedef struct _GtkWindow GtkWindow;
 
-class Extension;
 class Profile;
 class TabContentsWrapper;
 
+namespace extensions{
+class Extension;
+}
+
 class CreateApplicationShortcutsDialogGtk
     : public base::RefCountedThreadSafe<CreateApplicationShortcutsDialogGtk,
                                         BrowserThread::DeleteOnUIThread> {
@@ -103,11 +106,12 @@ class CreateChromeApplicationShortcutsDialogGtk
     public ImageLoadingTracker::Observer {
  public:
   // Displays the dialog box to create application shortcuts for |app|.
-  static void Show(GtkWindow* parent, Profile* profile, const Extension* app);
+  static void Show(GtkWindow* parent, Profile* profile,
+                   const extensions::Extension* app);
 
   CreateChromeApplicationShortcutsDialogGtk(GtkWindow* parent,
                                             Profile* profile,
-                                            const Extension* app);
+                                            const extensions::Extension* app);
 
   // Implement ImageLoadingTracker::Observer.  |tracker_| is used to
   // load the app's icon.  This method recieves the icon, and adds
@@ -123,7 +127,7 @@ class CreateChromeApplicationShortcutsDialogGtk
       const ShellIntegration::ShortcutInfo& shortcut_info) OVERRIDE;
 
  private:
-  const Extension* app_;
+  const extensions::Extension* app_;
   FilePath profile_path_;
   ImageLoadingTracker tracker_;
   DISALLOW_COPY_AND_ASSIGN(CreateChromeApplicationShortcutsDialogGtk);
diff --git a/chrome/browser/ui/gtk/extensions/extension_installed_bubble_gtk.cc b/chrome/browser/ui/gtk/extensions/extension_installed_bubble_gtk.cc
index 6ca7c08..b9ae719 100644
--- a/chrome/browser/ui/gtk/extensions/extension_installed_bubble_gtk.cc
+++ b/chrome/browser/ui/gtk/extensions/extension_installed_bubble_gtk.cc
@@ -31,6 +31,8 @@
 #include "ui/base/resource/resource_bundle.h"
 #include "ui/gfx/gtk_util.h"
 
+using extensions::Extension;
+
 namespace {
 
 const int kHorizontalColumnSpacing = 10;
@@ -115,7 +117,7 @@ void ExtensionInstalledBubbleGtk::Observe(
     }
   } else if (type == chrome::NOTIFICATION_EXTENSION_UNLOADED) {
     const Extension* extension =
-        content::Details<UnloadedExtensionInfo>(details)->extension;
+        content::Details<extensions::UnloadedExtensionInfo>(details)->extension;
     if (extension == extension_)
       extension_ = NULL;
   } else {
diff --git a/chrome/browser/ui/gtk/extensions/extension_installed_bubble_gtk.h b/chrome/browser/ui/gtk/extensions/extension_installed_bubble_gtk.h
index cf21723..54f9d06 100644
--- a/chrome/browser/ui/gtk/extensions/extension_installed_bubble_gtk.h
+++ b/chrome/browser/ui/gtk/extensions/extension_installed_bubble_gtk.h
@@ -16,9 +16,12 @@
 #include "third_party/skia/include/core/SkBitmap.h"
 
 class Browser;
-class Extension;
 class SkBitmap;
 
+namespace extensions {
+class Extension;
+}
+
 // Provides feedback to the user upon successful installation of an
 // extension. Depending on the type of extension, the BubbleGtk will
 // point to:
@@ -47,14 +50,16 @@ class ExtensionInstalledBubbleGtk
   // the extension has loaded. |extension| is the installed extension. |browser|
   // is the browser window which will host the bubble. |icon| is the install
   // icon of the extension.
-  static void Show(
-      const Extension* extension, Browser *browser, const SkBitmap& icon);
+  static void Show(const extensions::Extension* extension,
+                   Browser *browser,
+                   const SkBitmap& icon);
 
  private:
   friend class base::RefCountedThreadSafe<ExtensionInstalledBubbleGtk>;
 
   // Private ctor. Registers a listener for EXTENSION_LOADED.
-  ExtensionInstalledBubbleGtk(const Extension* extension, Browser *browser,
+  ExtensionInstalledBubbleGtk(const extensions::Extension* extension,
+                              Browser *browser,
                               const SkBitmap& icon);
 
   virtual ~ExtensionInstalledBubbleGtk();
@@ -76,7 +81,7 @@ class ExtensionInstalledBubbleGtk
   static void OnButtonClick(GtkWidget* button,
                             ExtensionInstalledBubbleGtk* toolbar);
 
-  const Extension* extension_;
+  const extensions::Extension* extension_;
   Browser* browser_;
   SkBitmap icon_;
   content::NotificationRegistrar registrar_;
diff --git a/chrome/browser/ui/gtk/extensions/extension_keybinding_registry_gtk.cc b/chrome/browser/ui/gtk/extensions/extension_keybinding_registry_gtk.cc
index d3709df..39c8c3b 100644
--- a/chrome/browser/ui/gtk/extensions/extension_keybinding_registry_gtk.cc
+++ b/chrome/browser/ui/gtk/extensions/extension_keybinding_registry_gtk.cc
@@ -43,7 +43,7 @@ gboolean ExtensionKeybindingRegistryGtk::HasPriorityHandler(
 }
 
 void ExtensionKeybindingRegistryGtk::AddExtensionKeybinding(
-    const Extension* extension) {
+    const extensions::Extension* extension) {
   ExtensionCommandService* command_service =
       ExtensionCommandServiceFactory::GetForProfile(profile_);
   const extensions::CommandMap& commands =
@@ -97,7 +97,7 @@ void ExtensionKeybindingRegistryGtk::AddExtensionKeybinding(
 }
 
 void ExtensionKeybindingRegistryGtk::RemoveExtensionKeybinding(
-    const Extension* extension) {
+    const extensions::Extension* extension) {
   EventTargets::iterator iter = event_targets_.begin();
   while (iter != event_targets_.end()) {
     if (iter->second.first != extension->id()) {
diff --git a/chrome/browser/ui/gtk/extensions/extension_keybinding_registry_gtk.h b/chrome/browser/ui/gtk/extensions/extension_keybinding_registry_gtk.h
index 41d0006..e17977c 100644
--- a/chrome/browser/ui/gtk/extensions/extension_keybinding_registry_gtk.h
+++ b/chrome/browser/ui/gtk/extensions/extension_keybinding_registry_gtk.h
@@ -14,9 +14,12 @@
 #include "ui/base/accelerators/accelerator_gtk.h"
 #include "ui/base/gtk/gtk_signal.h"
 
-class Extension;
 class Profile;
 
+namespace extensions {
+class Extension;
+}
+
 typedef struct _GtkAccelGroup GtkAccelGroup;
 typedef struct _GdkEventKey GdkEventKey;
 
@@ -42,8 +45,10 @@ class ExtensionKeybindingRegistryGtk
 
  protected:
   // Overridden from ExtensionKeybindingRegistry:
-  virtual void AddExtensionKeybinding(const Extension* extension) OVERRIDE;
-  virtual void RemoveExtensionKeybinding(const Extension* extension) OVERRIDE;
+  virtual void AddExtensionKeybinding(
+      const extensions::Extension* extension) OVERRIDE;
+  virtual void RemoveExtensionKeybinding(
+      const extensions::Extension* extension) OVERRIDE;
 
  private:
   // The accelerator handler for when the extension command shortcuts are
diff --git a/chrome/browser/ui/gtk/extensions/shell_window_gtk.cc b/chrome/browser/ui/gtk/extensions/shell_window_gtk.cc
index 04aaf78..466a217 100644
--- a/chrome/browser/ui/gtk/extensions/shell_window_gtk.cc
+++ b/chrome/browser/ui/gtk/extensions/shell_window_gtk.cc
@@ -13,7 +13,7 @@
 #include "ui/gfx/rect.h"
 
 ShellWindowGtk::ShellWindowGtk(Profile* profile,
-                               const Extension* extension,
+                               const extensions::Extension* extension,
                                const GURL& url)
     : ShellWindow(profile, extension, url),
       state_(GDK_WINDOW_STATE_WITHDRAWN),
@@ -168,7 +168,7 @@ gboolean ShellWindowGtk::OnWindowState(GtkWidget* sender,
 
 // static
 ShellWindow* ShellWindow::CreateImpl(Profile* profile,
-                                     const Extension* extension,
+                                     const extensions::Extension* extension,
                                      const GURL& url) {
   return new ShellWindowGtk(profile, extension, url);
 }
diff --git a/chrome/browser/ui/gtk/extensions/shell_window_gtk.h b/chrome/browser/ui/gtk/extensions/shell_window_gtk.h
index 1e14c89..6705ec9 100644
--- a/chrome/browser/ui/gtk/extensions/shell_window_gtk.h
+++ b/chrome/browser/ui/gtk/extensions/shell_window_gtk.h
@@ -16,12 +16,16 @@
 
 class Profile;
 
+namespace extensions {
+class Extension;
+}
+
 class ShellWindowGtk : public ShellWindow,
                        public ExtensionViewGtk::Container,
                        public ui::ActiveWindowWatcherXObserver {
  public:
   ShellWindowGtk(Profile* profile,
-                 const Extension* extension,
+                 const extensions::Extension* extension,
                  const GURL& url);
 
   // BaseWindow implementation.
diff --git a/chrome/browser/ui/gtk/gtk_theme_service.cc b/chrome/browser/ui/gtk/gtk_theme_service.cc
index 3b74081..a9123a9 100644
--- a/chrome/browser/ui/gtk/gtk_theme_service.cc
+++ b/chrome/browser/ui/gtk/gtk_theme_service.cc
@@ -25,6 +25,7 @@
 #include "chrome/browser/ui/gtk/gtk_util.h"
 #include "chrome/browser/ui/gtk/hover_controller_gtk.h"
 #include "chrome/common/chrome_notification_types.h"
+#include "chrome/common/extensions/extension.h"
 #include "chrome/common/pref_names.h"
 #include "content/public/browser/notification_details.h"
 #include "content/public/browser/notification_service.h"
@@ -346,7 +347,7 @@ void GtkThemeService::InitThemesFor(NotificationObserver* observer) {
                     content::NotificationService::NoDetails());
 }
 
-void GtkThemeService::SetTheme(const Extension* extension) {
+void GtkThemeService::SetTheme(const extensions::Extension* extension) {
   profile()->GetPrefs()->SetBoolean(prefs::kUsesSystemTheme, false);
   LoadDefaultValues();
   ThemeService::SetTheme(extension);
diff --git a/chrome/browser/ui/gtk/gtk_theme_service.h b/chrome/browser/ui/gtk/gtk_theme_service.h
index d421ffb..d253aa0 100644
--- a/chrome/browser/ui/gtk/gtk_theme_service.h
+++ b/chrome/browser/ui/gtk/gtk_theme_service.h
@@ -21,6 +21,10 @@
 
 class Profile;
 
+namespace extensions {
+class Extension;
+}
+
 namespace gfx {
 class CairoCachedSurface;
 }
@@ -68,7 +72,7 @@ class GtkThemeService : public ThemeService {
   virtual const gfx::Image* GetImageNamed(int id) const OVERRIDE;
   virtual SkColor GetColor(int id) const OVERRIDE;
   virtual bool HasCustomImage(int id) const OVERRIDE;
-  virtual void SetTheme(const Extension* extension) OVERRIDE;
+  virtual void SetTheme(const extensions::Extension* extension) OVERRIDE;
   virtual void UseDefaultTheme() OVERRIDE;
   virtual void SetNativeTheme() OVERRIDE;
   virtual bool UsingDefaultTheme() const OVERRIDE;
diff --git a/chrome/browser/ui/gtk/infobars/extension_infobar_gtk.cc b/chrome/browser/ui/gtk/infobars/extension_infobar_gtk.cc
index b78d006..cdac8db 100644
--- a/chrome/browser/ui/gtk/infobars/extension_infobar_gtk.cc
+++ b/chrome/browser/ui/gtk/infobars/extension_infobar_gtk.cc
@@ -109,7 +109,8 @@ void ExtensionInfoBarGtk::BuildWidgets() {
   gtk_util::CenterWidgetInHBox(hbox_, button_, false, 0);
 
   // Start loading the image for the menu button.
-  const Extension* extension = delegate_->extension_host()->extension();
+  const extensions::Extension* extension = delegate_->extension_host()->
+      extension();
   ExtensionResource icon_resource = extension->GetIconResource(
       ExtensionIconSet::EXTENSION_ICON_BITTY, ExtensionIconSet::MATCH_EXACTLY);
   // Create a tracker to load the image. It will report back on OnImageLoaded.
@@ -154,7 +155,7 @@ Browser* ExtensionInfoBarGtk::GetBrowser() {
 }
 
 ui::MenuModel* ExtensionInfoBarGtk::BuildMenuModel() {
-  const Extension* extension = delegate_->extension();
+  const extensions::Extension* extension = delegate_->extension();
   if (!extension->ShowConfigureContextMenus())
     return NULL;
 
diff --git a/chrome/browser/ui/gtk/location_bar_view_gtk.cc b/chrome/browser/ui/gtk/location_bar_view_gtk.cc
index 3b8cdfc..fbd73a8 100644
--- a/chrome/browser/ui/gtk/location_bar_view_gtk.cc
+++ b/chrome/browser/ui/gtk/location_bar_view_gtk.cc
@@ -84,6 +84,7 @@ using content::NavigationEntry;
 using content::OpenURLParams;
 using content::WebContents;
 using extensions::ActionBoxController;
+using extensions::Extension;
 
 namespace {
 
diff --git a/chrome/browser/ui/intents/web_intent_picker_controller_browsertest.cc b/chrome/browser/ui/intents/web_intent_picker_controller_browsertest.cc
index df67227..6528dab 100644
--- a/chrome/browser/ui/intents/web_intent_picker_controller_browsertest.cc
+++ b/chrome/browser/ui/intents/web_intent_picker_controller_browsertest.cc
@@ -463,8 +463,8 @@ IN_PROC_BROWSER_TEST_F(WebIntentPickerControllerBrowserTest,
   OnExtensionInstallRequested(extension_id);
   picker_.Wait();
   EXPECT_EQ(1, picker_.num_extensions_installed_);
-  const Extension* extension = browser()->profile()->GetExtensionService()->
-      GetExtensionById(extension_id, false);
+  const extensions::Extension* extension = browser()->profile()->
+      GetExtensionService()->GetExtensionById(extension_id, false);
   EXPECT_TRUE(extension);
 
   // Installing an extension should also choose it. Since this extension uses
diff --git a/chrome/browser/ui/panels/base_panel_browser_test.cc b/chrome/browser/ui/panels/base_panel_browser_test.cc
index a6df5ee..c7a2e25 100644
--- a/chrome/browser/ui/panels/base_panel_browser_test.cc
+++ b/chrome/browser/ui/panels/base_panel_browser_test.cc
@@ -40,6 +40,7 @@
 #endif
 
 using content::WebContentsTester;
+using extensions::Extension;
 
 namespace {
 
diff --git a/chrome/browser/ui/panels/base_panel_browser_test.h b/chrome/browser/ui/panels/base_panel_browser_test.h
index 8afc099..eca8bbb 100644
--- a/chrome/browser/ui/panels/base_panel_browser_test.h
+++ b/chrome/browser/ui/panels/base_panel_browser_test.h
@@ -92,9 +92,10 @@ class BasePanelBrowserTest : public InProcessBrowserTest {
 
   void CreateTestTabContents(Browser* browser);
 
-  scoped_refptr<Extension> CreateExtension(const FilePath::StringType& path,
-                                           Extension::Location location,
-                                           const DictionaryValue& extra_value);
+  scoped_refptr<extensions::Extension> CreateExtension(
+      const FilePath::StringType& path,
+      extensions::Extension::Location location,
+      const DictionaryValue& extra_value);
 
   void MoveMouseAndWaitForExpansionStateChange(Panel* panel,
                                                const gfx::Point& position);
diff --git a/chrome/browser/ui/panels/panel.cc b/chrome/browser/ui/panels/panel.cc
index e4f54d1..f9a8db8 100644
--- a/chrome/browser/ui/panels/panel.cc
+++ b/chrome/browser/ui/panels/panel.cc
@@ -602,7 +602,7 @@ void Panel::ShowCreateWebAppShortcutsDialog(TabContentsWrapper* tab_contents) {
 }
 
 void Panel::ShowCreateChromeAppShortcutsDialog(Profile* profile,
-                                               const Extension* app) {
+    const extensions::Extension* app) {
   NOTIMPLEMENTED();
 }
 
diff --git a/chrome/browser/ui/panels/panel.h b/chrome/browser/ui/panels/panel.h
index 9f2eaca..363c6a5 100644
--- a/chrome/browser/ui/panels/panel.h
+++ b/chrome/browser/ui/panels/panel.h
@@ -20,6 +20,10 @@ class NativePanel;
 class PanelManager;
 class PanelStrip;
 
+namespace extensions {
+class Extension;
+}
+
 // A platform independent implementation of BrowserWindow for Panels.  This
 // class would get the first crack at all the BrowserWindow calls for Panels and
 // do one or more of the following:
@@ -175,7 +179,7 @@ class Panel : public BrowserWindow,
   virtual void ShowCreateWebAppShortcutsDialog(
       TabContentsWrapper* tab_contents) OVERRIDE;
   virtual void ShowCreateChromeAppShortcutsDialog(
-      Profile* profile, const Extension* app) OVERRIDE;
+      Profile* profile, const extensions::Extension* app) OVERRIDE;
   virtual void Cut() OVERRIDE;
   virtual void Copy() OVERRIDE;
   virtual void Paste() OVERRIDE;
diff --git a/chrome/browser/ui/panels/panel_app_browsertest.cc b/chrome/browser/ui/panels/panel_app_browsertest.cc
index 541aef5..ba3b086d 100644
--- a/chrome/browser/ui/panels/panel_app_browsertest.cc
+++ b/chrome/browser/ui/panels/panel_app_browsertest.cc
@@ -42,7 +42,7 @@ class PanelAppBrowserTest : public ExtensionBrowserTest {
     EXPECT_TRUE(LoadExtension(test_data_dir_.AppendASCII(name)));
 
     ExtensionService* service = browser()->profile()->GetExtensionService();
-    const Extension* extension = service->GetExtensionById(
+    const extensions::Extension* extension = service->GetExtensionById(
         last_loaded_extension_id_, false);
     EXPECT_TRUE(extension);
 
diff --git a/chrome/browser/ui/panels/panel_browser_frame_view.h b/chrome/browser/ui/panels/panel_browser_frame_view.h
index 953b19c..bc542a8 100644
--- a/chrome/browser/ui/panels/panel_browser_frame_view.h
+++ b/chrome/browser/ui/panels/panel_browser_frame_view.h
@@ -13,7 +13,6 @@
 #include "chrome/browser/ui/views/tab_icon_view.h"
 #include "ui/views/controls/button/button.h"
 
-class Extension;
 class PanelBrowserView;
 class SkPaint;
 namespace gfx {
diff --git a/chrome/browser/ui/panels/panel_browsertest.cc b/chrome/browser/ui/panels/panel_browsertest.cc
index 87f4681..4068b7a 100644
--- a/chrome/browser/ui/panels/panel_browsertest.cc
+++ b/chrome/browser/ui/panels/panel_browsertest.cc
@@ -50,6 +50,7 @@ using content::BrowserThread;
 using content::DownloadItem;
 using content::DownloadManager;
 using content::WebContents;
+using extensions::Extension;
 
 class PanelBrowserTest : public BasePanelBrowserTest {
  public:
@@ -1332,12 +1333,12 @@ IN_PROC_BROWSER_TEST_F(PanelBrowserTest,
       content::Source<Browser>(panel1->browser()));
 
   // Send unload notification on the first extension.
-  UnloadedExtensionInfo details(extension,
+  extensions::UnloadedExtensionInfo details(extension,
                                 extension_misc::UNLOAD_REASON_UNINSTALL);
   content::NotificationService::current()->Notify(
       chrome::NOTIFICATION_EXTENSION_UNLOADED,
       content::Source<Profile>(browser()->profile()),
-      content::Details<UnloadedExtensionInfo>(&details));
+      content::Details<extensions::UnloadedExtensionInfo>(&details));
 
   // Wait for the panels opened by the first extension to close.
   signal.Wait();
diff --git a/chrome/browser/ui/startup/startup_browser_creator_browsertest.cc b/chrome/browser/ui/startup/startup_browser_creator_browsertest.cc
index 8f83a6a..e13e32d 100644
--- a/chrome/browser/ui/startup/startup_browser_creator_browsertest.cc
+++ b/chrome/browser/ui/startup/startup_browser_creator_browsertest.cc
@@ -31,6 +31,8 @@
 #include "content/public/browser/web_contents.h"
 #include "testing/gtest/include/gtest/gtest.h"
 
+using extensions::Extension;
+
 class StartupBrowserCreatorTest : public ExtensionBrowserTest {
  protected:
   virtual bool SetUpUserDataDirectory() OVERRIDE {
diff --git a/chrome/browser/ui/startup/startup_browser_creator_impl.cc b/chrome/browser/ui/startup/startup_browser_creator_impl.cc
index bcf88f8..fca8b92 100644
--- a/chrome/browser/ui/startup/startup_browser_creator_impl.cc
+++ b/chrome/browser/ui/startup/startup_browser_creator_impl.cc
@@ -89,6 +89,7 @@
 
 using content::ChildProcessSecurityPolicy;
 using content::WebContents;
+using extensions::Extension;
 using protector::ProtectedPrefsWatcher;
 using protector::ProtectorService;
 using protector::ProtectorServiceFactory;
diff --git a/chrome/browser/ui/tabs/pinned_tab_codec.cc b/chrome/browser/ui/tabs/pinned_tab_codec.cc
index 849033a..00258dc 100644
--- a/chrome/browser/ui/tabs/pinned_tab_codec.cc
+++ b/chrome/browser/ui/tabs/pinned_tab_codec.cc
@@ -54,7 +54,7 @@ static void EncodePinnedTab(TabStripModel* model,
 
   TabContentsWrapper* tab_contents = model->GetTabContentsAt(index);
   if (model->IsAppTab(index)) {
-    const Extension* extension =
+    const extensions::Extension* extension =
         tab_contents->extension_tab_helper()->extension_app();
     DCHECK(extension);
     value->SetString(kAppID, extension->id());
diff --git a/chrome/browser/ui/tabs/tab_strip_model.cc b/chrome/browser/ui/tabs/tab_strip_model.cc
index bf8b302..d7d600a2 100644
--- a/chrome/browser/ui/tabs/tab_strip_model.cc
+++ b/chrome/browser/ui/tabs/tab_strip_model.cc
@@ -1020,8 +1020,9 @@ void TabStripModel::Observe(int type,
     }
 
     case chrome::NOTIFICATION_EXTENSION_UNLOADED: {
-      const Extension* extension =
-          content::Details<UnloadedExtensionInfo>(details)->extension;
+      const extensions::Extension* extension =
+          content::Details<extensions::UnloadedExtensionInfo>(
+              details)->extension;
       // Iterate backwards as we may remove items while iterating.
       for (int i = count() - 1; i >= 0; i--) {
         TabContentsWrapper* contents = GetTabContentsAt(i);
diff --git a/chrome/browser/ui/tabs/tab_strip_model_unittest.cc b/chrome/browser/ui/tabs/tab_strip_model_unittest.cc
index e9b4153..b8099f1 100644
--- a/chrome/browser/ui/tabs/tab_strip_model_unittest.cc
+++ b/chrome/browser/ui/tabs/tab_strip_model_unittest.cc
@@ -46,6 +46,7 @@ using content::BrowserThread;
 using content::NavigationController;
 using content::SiteInstance;
 using content::WebContents;
+using extensions::Extension;
 using testing::_;
 
 namespace {
diff --git a/chrome/browser/ui/views/ash/app_list/app_list_model_builder.cc b/chrome/browser/ui/views/ash/app_list/app_list_model_builder.cc
index ce6c67f..a660105 100644
--- a/chrome/browser/ui/views/ash/app_list/app_list_model_builder.cc
+++ b/chrome/browser/ui/views/ash/app_list/app_list_model_builder.cc
@@ -23,6 +23,8 @@
 #include "ui/base/l10n/l10n_util_collator.h"
 #include "ui/base/resource/resource_bundle.h"
 
+using extensions::Extension;
+
 namespace {
 
 const char* kSpecialApps[] = {
@@ -251,7 +253,8 @@ void AppListModelBuilder::Observe(int type,
     }
     case chrome::NOTIFICATION_EXTENSION_UNLOADED: {
       const Extension* extension =
-          content::Details<UnloadedExtensionInfo>(details)->extension;
+          content::Details<extensions::UnloadedExtensionInfo>(
+              details)->extension;
       int index = FindApp(extension->id());
       if (index >= 0)
         model_->DeleteItemAt(index);
diff --git a/chrome/browser/ui/views/ash/app_list/extension_app_item.cc b/chrome/browser/ui/views/ash/app_list/extension_app_item.cc
index 6aef8c7..632887b 100644
--- a/chrome/browser/ui/views/ash/app_list/extension_app_item.cc
+++ b/chrome/browser/ui/views/ash/app_list/extension_app_item.cc
@@ -21,6 +21,8 @@
 #include "ui/base/l10n/l10n_util.h"
 #include "ui/gfx/image/image.h"
 
+using extensions::Extension;
+
 namespace {
 
 enum CommandId {
diff --git a/chrome/browser/ui/views/ash/app_list/extension_app_item.h b/chrome/browser/ui/views/ash/app_list/extension_app_item.h
index 3621ded..c4dcdf8 100644
--- a/chrome/browser/ui/views/ash/app_list/extension_app_item.h
+++ b/chrome/browser/ui/views/ash/app_list/extension_app_item.h
@@ -13,22 +13,25 @@
 #include "chrome/browser/ui/views/ash/app_list/chrome_app_list_item.h"
 #include "ui/base/models/simple_menu_model.h"
 
-class Extension;
 class ExtensionResource;
 class Profile;
 class SkBitmap;
 
+namespace extensions {
+class Extension;
+}
+
 // ExtensionAppItem represents an extension app in app list.
 class ExtensionAppItem : public ChromeAppListItem,
                          public ImageLoadingTracker::Observer,
                          public ui::SimpleMenuModel::Delegate {
  public:
-  ExtensionAppItem(Profile* profile, const Extension* extension);
+  ExtensionAppItem(Profile* profile, const extensions::Extension* extension);
   virtual ~ExtensionAppItem();
 
   // Gets extension associated with this model. Returns NULL if extension
   // no longer exists.
-  const Extension* GetExtension() const;
+  const extensions::Extension* GetExtension() const;
 
   const std::string& extension_id() const {
     return extension_id_;
@@ -36,7 +39,7 @@ class ExtensionAppItem : public ChromeAppListItem,
 
  private:
   // Loads extension icon.
-  void LoadImage(const Extension* extension);
+  void LoadImage(const extensions::Extension* extension);
 
   void ShowExtensionOptions();
   void StartExtensionUninstall();
diff --git a/chrome/browser/ui/views/ash/extension_utils.cc b/chrome/browser/ui/views/ash/extension_utils.cc
index c31411b..3e3633e 100644
--- a/chrome/browser/ui/views/ash/extension_utils.cc
+++ b/chrome/browser/ui/views/ash/extension_utils.cc
@@ -17,7 +17,7 @@ namespace extension_utils {
 // Opens an extension.  |event_flags| holds the flags of the event
 // which invokes this extension.
 void OpenExtension(Profile* profile,
-                   const Extension* extension,
+                   const extensions::Extension* extension,
                    int event_flags) {
   DCHECK(profile);
   DCHECK(extension);
diff --git a/chrome/browser/ui/views/ash/extension_utils.h b/chrome/browser/ui/views/ash/extension_utils.h
index 95d4f76..f38f030 100644
--- a/chrome/browser/ui/views/ash/extension_utils.h
+++ b/chrome/browser/ui/views/ash/extension_utils.h
@@ -7,14 +7,17 @@
 #pragma once
 
 class Profile;
+
+namespace extensions {
 class Extension;
+}
 
 namespace extension_utils {
 
 // Opens an extension.  |event_flags| holds the flags of the event
 // which triggered this extension.
 void OpenExtension(Profile* profile,
-                   const Extension* extension,
+                   const extensions::Extension* extension,
                    int event_flags);
 
 }  // namespace extension_utils
diff --git a/chrome/browser/ui/views/ash/launcher/browser_launcher_item_controller.cc b/chrome/browser/ui/views/ash/launcher/browser_launcher_item_controller.cc
index 3563c3c..6fba790 100644
--- a/chrome/browser/ui/views/ash/launcher/browser_launcher_item_controller.cc
+++ b/chrome/browser/ui/views/ash/launcher/browser_launcher_item_controller.cc
@@ -188,7 +188,7 @@ void BrowserLauncherItemController::UpdateLauncher(TabContentsWrapper* tab) {
     if (!new_image.empty())
       item.image = new_image;
     else if (item.image.empty())
-      item.image = Extension::GetDefaultIcon(true);
+      item.image = extensions::Extension::GetDefaultIcon(true);
   } else {
     DCHECK_EQ(TYPE_TABBED, type_);
     ui::ResourceBundle& rb = ui::ResourceBundle::GetSharedInstance();
diff --git a/chrome/browser/ui/views/ash/launcher/chrome_launcher_controller.cc b/chrome/browser/ui/views/ash/launcher/chrome_launcher_controller.cc
index 6ca146e..96ca234 100644
--- a/chrome/browser/ui/views/ash/launcher/chrome_launcher_controller.cc
+++ b/chrome/browser/ui/views/ash/launcher/chrome_launcher_controller.cc
@@ -39,6 +39,8 @@
 #include "ui/aura/window.h"
 #include "ui/views/widget/widget.h"
 
+using extensions::Extension;
+
 namespace {
 
 // Values used for prefs::kShelfAutoHideBehavior.
@@ -534,7 +536,8 @@ void ChromeLauncherController::Observe(
     }
     case chrome::NOTIFICATION_EXTENSION_UNLOADED: {
       const Extension* extension =
-          content::Details<UnloadedExtensionInfo>(details)->extension;
+          content::Details<extensions::UnloadedExtensionInfo>(
+              details)->extension;
       if (IsAppPinned(extension->id())) {
         // TODO(dpolukhin): also we need to remember index of the app to show
         // it on the same place when it gets loaded again.
diff --git a/chrome/browser/ui/views/ash/launcher/chrome_launcher_controller_unittest.cc b/chrome/browser/ui/views/ash/launcher/chrome_launcher_controller_unittest.cc
index 9c47f9c..deb821c 100644
--- a/chrome/browser/ui/views/ash/launcher/chrome_launcher_controller_unittest.cc
+++ b/chrome/browser/ui/views/ash/launcher/chrome_launcher_controller_unittest.cc
@@ -19,6 +19,8 @@
 #include "testing/gmock/include/gmock/gmock.h"
 #include "testing/gtest/include/gtest/gtest.h"
 
+using extensions::Extension;
+
 class ChromeLauncherControllerTest : public testing::Test {
  protected:
   ChromeLauncherControllerTest()
diff --git a/chrome/browser/ui/views/ash/launcher/launcher_app_icon_loader.cc b/chrome/browser/ui/views/ash/launcher/launcher_app_icon_loader.cc
index 9d0ac08..12f8839 100644
--- a/chrome/browser/ui/views/ash/launcher/launcher_app_icon_loader.cc
+++ b/chrome/browser/ui/views/ash/launcher/launcher_app_icon_loader.cc
@@ -22,7 +22,7 @@ LauncherAppIconLoader::~LauncherAppIconLoader() {
 }
 
 std::string LauncherAppIconLoader::GetAppID(TabContentsWrapper* tab) {
-  const Extension* extension = GetExtensionForTab(tab);
+  const extensions::Extension* extension = GetExtensionForTab(tab);
   return extension ? extension->id() : std::string();
 }
 
@@ -37,7 +37,7 @@ void LauncherAppIconLoader::FetchImage(const std::string& id) {
       return;  // Already loading the image.
   }
 
-  const Extension* extension = GetExtensionByID(id);
+  const extensions::Extension* extension = GetExtensionByID(id);
   if (!extension)
     return;
   if (!image_loader_.get())
@@ -67,7 +67,7 @@ void LauncherAppIconLoader::OnImageLoaded(const gfx::Image& image,
     host_->SetAppImage(id, image.ToSkBitmap());
 }
 
-const Extension* LauncherAppIconLoader::GetExtensionForTab(
+const extensions::Extension* LauncherAppIconLoader::GetExtensionForTab(
     TabContentsWrapper* tab) {
   ExtensionService* extension_service = profile_->GetExtensionService();
   if (!extension_service)
@@ -75,7 +75,7 @@ const Extension* LauncherAppIconLoader::GetExtensionForTab(
   return extension_service->GetInstalledApp(tab->web_contents()->GetURL());
 }
 
-const Extension* LauncherAppIconLoader::GetExtensionByID(
+const extensions::Extension* LauncherAppIconLoader::GetExtensionByID(
     const std::string& id) {
   ExtensionService* service = profile_->GetExtensionService();
   if (!service)
diff --git a/chrome/browser/ui/views/ash/launcher/launcher_app_icon_loader.h b/chrome/browser/ui/views/ash/launcher/launcher_app_icon_loader.h
index 1740f5a..ff26b42 100644
--- a/chrome/browser/ui/views/ash/launcher/launcher_app_icon_loader.h
+++ b/chrome/browser/ui/views/ash/launcher/launcher_app_icon_loader.h
@@ -13,9 +13,13 @@
 #include "chrome/browser/extensions/image_loading_tracker.h"
 #include "chrome/browser/ui/views/ash/launcher/chrome_launcher_controller.h"
 
-class Extension;
 class Profile;
 
+namespace extensions {
+class Extension;
+}
+
+
 // Default implementation of LauncherUpdater::AppIconLoader that interacts
 // with the ExtensionService and ImageLoadingTracker to load images.
 class LauncherAppIconLoader : public ChromeLauncherController::AppIconLoader,
@@ -38,10 +42,10 @@ class LauncherAppIconLoader : public ChromeLauncherController::AppIconLoader,
   typedef std::map<int, std::string> ImageLoaderIDToExtensionIDMap;
 
   // Returns the extension for the specified tab.
-  const Extension* GetExtensionForTab(TabContentsWrapper* tab);
+  const extensions::Extension* GetExtensionForTab(TabContentsWrapper* tab);
 
   // Returns the extension by ID.
-  const Extension* GetExtensionByID(const std::string& id);
+  const extensions::Extension* GetExtensionByID(const std::string& id);
 
   Profile* profile_;
 
diff --git a/chrome/browser/ui/views/browser_actions_container.cc b/chrome/browser/ui/views/browser_actions_container.cc
index 5fb9050..04fb9e8 100644
--- a/chrome/browser/ui/views/browser_actions_container.cc
+++ b/chrome/browser/ui/views/browser_actions_container.cc
@@ -55,6 +55,8 @@
 #include "ui/views/controls/resize_area.h"
 #include "ui/views/metrics.h"
 
+using extensions::Extension;
+
 namespace {
 
 // Horizontal spacing between most items in the container, as well as after the
@@ -483,8 +485,8 @@ void BrowserActionsContainer::CreateBrowserActionViews() {
   if (!model_)
     return;
 
-  for (ExtensionList::iterator iter = model_->begin(); iter != model_->end();
-       ++iter) {
+  for (extensions::ExtensionList::iterator iter = model_->begin();
+       iter != model_->end(); ++iter) {
     if (!ShouldDisplayBrowserAction(*iter))
       continue;
 
diff --git a/chrome/browser/ui/views/browser_actions_container.h b/chrome/browser/ui/views/browser_actions_container.h
index d1677f7..b88c6a9 100644
--- a/chrome/browser/ui/views/browser_actions_container.h
+++ b/chrome/browser/ui/views/browser_actions_container.h
@@ -33,12 +33,15 @@
 
 class Browser;
 class BrowserActionsContainer;
-class Extension;
 class ExtensionAction;
 class ExtensionPopup;
 class PrefService;
 class Profile;
 
+namespace extensions {
+class Extension;
+}
+
 namespace ui {
 class SlideAnimation;
 }
@@ -59,14 +62,14 @@ class BrowserActionButton : public views::MenuButton,
                             public ImageLoadingTracker::Observer,
                             public content::NotificationObserver {
  public:
-  BrowserActionButton(const Extension* extension,
+  BrowserActionButton(const extensions::Extension* extension,
                       BrowserActionsContainer* panel);
 
   // Call this instead of delete.
   void Destroy();
 
   ExtensionAction* browser_action() const { return browser_action_; }
-  const Extension* extension() { return extension_; }
+  const extensions::Extension* extension() { return extension_; }
 
   // Called to update the display to match the browser action's state.
   void UpdateState();
@@ -127,7 +130,7 @@ class BrowserActionButton : public views::MenuButton,
   ExtensionAction* browser_action_;
 
   // The extension associated with the browser action we're displaying.
-  const Extension* extension_;
+  const extensions::Extension* extension_;
 
   // The object that is waiting for the image loading to complete
   // asynchronously.
@@ -162,7 +165,8 @@ class BrowserActionButton : public views::MenuButton,
 
 class BrowserActionView : public views::View {
  public:
-  BrowserActionView(const Extension* extension, BrowserActionsContainer* panel);
+  BrowserActionView(const extensions::Extension* extension,
+                    BrowserActionsContainer* panel);
   virtual ~BrowserActionView();
 
   BrowserActionButton* button() { return button_; }
@@ -406,10 +410,11 @@ class BrowserActionsContainer
   static int IconHeight();
 
   // ExtensionToolbarModel::Observer implementation.
-  virtual void BrowserActionAdded(const Extension* extension,
+  virtual void BrowserActionAdded(const extensions::Extension* extension,
                                   int index) OVERRIDE;
-  virtual void BrowserActionRemoved(const Extension* extension) OVERRIDE;
-  virtual void BrowserActionMoved(const Extension* extension,
+  virtual void BrowserActionRemoved(
+      const extensions::Extension* extension) OVERRIDE;
+  virtual void BrowserActionMoved(const extensions::Extension* extension,
                                   int index) OVERRIDE;
   virtual void ModelLoaded() OVERRIDE;
 
@@ -459,7 +464,7 @@ class BrowserActionsContainer
   // Returns true if this extension should be shown in this toolbar. This can
   // return false if we are in an incognito window and the extension is disabled
   // for incognito.
-  bool ShouldDisplayBrowserAction(const Extension* extension);
+  bool ShouldDisplayBrowserAction(const extensions::Extension* extension);
 
   // The vector of browser actions (icons/image buttons for each action). Note
   // that not every BrowserAction in the ToolbarModel will necessarily be in
diff --git a/chrome/browser/ui/views/browser_actions_container_browsertest.cc b/chrome/browser/ui/views/browser_actions_container_browsertest.cc
index a9e1e9a..3294ad4 100644
--- a/chrome/browser/ui/views/browser_actions_container_browsertest.cc
+++ b/chrome/browser/ui/views/browser_actions_container_browsertest.cc
@@ -11,6 +11,8 @@
 #include "chrome/common/extensions/extension_action.h"
 #include "chrome/common/extensions/extension_resource.h"
 
+using extensions::Extension;
+
 class BrowserActionsContainerTest : public ExtensionBrowserTest {
  public:
   BrowserActionsContainerTest() {
diff --git a/chrome/browser/ui/views/browser_dialogs.h b/chrome/browser/ui/views/browser_dialogs.h
index 16f8d1b..3a0a464 100644
--- a/chrome/browser/ui/views/browser_dialogs.h
+++ b/chrome/browser/ui/views/browser_dialogs.h
@@ -19,7 +19,6 @@
 
 class BrowserView;
 class EditSearchEngineControllerDelegate;
-class Extension;
 class FindBar;
 class GURL;
 class Profile;
@@ -30,6 +29,10 @@ namespace content {
 struct SSLStatus;
 }
 
+namespace extensions {
+class Extension;
+}
+
 namespace gfx {
 class Size;
 }
@@ -91,7 +94,7 @@ void ShowCreateWebAppShortcutsDialog(gfx::NativeWindow parent_window,
 // Shows the create chrome app shortcut dialog box.
 void ShowCreateChromeAppShortcutsDialog(gfx::NativeWindow parent_window,
                                         Profile* profile,
-                                        const Extension* app);
+                                        const extensions::Extension* app);
 
 }  // namespace browser
 
diff --git a/chrome/browser/ui/views/create_application_shortcut_view.cc b/chrome/browser/ui/views/create_application_shortcut_view.cc
index a627bc2..0e94c05 100644
--- a/chrome/browser/ui/views/create_application_shortcut_view.cc
+++ b/chrome/browser/ui/views/create_application_shortcut_view.cc
@@ -208,7 +208,7 @@ void ShowCreateWebAppShortcutsDialog(gfx::NativeWindow parent_window,
 
 void ShowCreateChromeAppShortcutsDialog(gfx::NativeWindow parent_window,
                                         Profile* profile,
-                                        const Extension* app) {
+                                        const extensions::Extension* app) {
   views::Widget::CreateWindowWithParent(
       new CreateChromeApplicationShortcutView(profile, app),
       parent_window)->Show();
@@ -482,7 +482,7 @@ void CreateUrlApplicationShortcutView::OnIconDownloaded(bool errored,
 
 CreateChromeApplicationShortcutView::CreateChromeApplicationShortcutView(
     Profile* profile,
-    const Extension* app) :
+    const extensions::Extension* app) :
       CreateApplicationShortcutView(profile),
       app_(app),
       ALLOW_THIS_IN_INITIALIZER_LIST(tracker_(this)) {
diff --git a/chrome/browser/ui/views/create_application_shortcut_view.h b/chrome/browser/ui/views/create_application_shortcut_view.h
index 8a49f9b..f7d5738 100644
--- a/chrome/browser/ui/views/create_application_shortcut_view.h
+++ b/chrome/browser/ui/views/create_application_shortcut_view.h
@@ -15,11 +15,14 @@
 #include "ui/views/controls/button/button.h"
 #include "ui/views/window/dialog_delegate.h"
 
-class Extension;
 class Profile;
 class TabContentsWrapper;
 class SkBitmap;
 
+namespace extensions {
+class Extension;
+}
+
 namespace views {
 class Checkbox;
 class Label;
@@ -110,7 +113,8 @@ class CreateChromeApplicationShortcutView
     : public CreateApplicationShortcutView,
      public ImageLoadingTracker::Observer {
  public:
-  CreateChromeApplicationShortcutView(Profile* profile, const Extension* app);
+  CreateChromeApplicationShortcutView(Profile* profile,
+                                      const extensions::Extension* app);
   virtual ~CreateChromeApplicationShortcutView();
 
   // Implement ImageLoadingTracker::Observer.  |tracker_| is used to
@@ -121,7 +125,7 @@ class CreateChromeApplicationShortcutView
                              int index) OVERRIDE;
 
  private:
-  const Extension* app_;
+  const extensions::Extension* app_;
   ImageLoadingTracker tracker_;
 
   DISALLOW_COPY_AND_ASSIGN(CreateChromeApplicationShortcutView);
diff --git a/chrome/browser/ui/views/extensions/browser_action_overflow_menu_controller.cc b/chrome/browser/ui/views/extensions/browser_action_overflow_menu_controller.cc
index e9fad5c..0f6b748 100644
--- a/chrome/browser/ui/views/extensions/browser_action_overflow_menu_controller.cc
+++ b/chrome/browser/ui/views/extensions/browser_action_overflow_menu_controller.cc
@@ -96,7 +96,7 @@ bool BrowserActionOverflowMenuController::ShowContextMenu(
     int id,
     const gfx::Point& p,
     bool is_mouse_gesture) {
-  const Extension* extension =
+  const extensions::Extension* extension =
       (*views_)[start_index_ + id - 1]->button()->extension();
   if (!extension->ShowConfigureContextMenus())
     return false;
diff --git a/chrome/browser/ui/views/extensions/extension_installed_bubble.cc b/chrome/browser/ui/views/extensions/extension_installed_bubble.cc
index acd3792..b36e673 100644
--- a/chrome/browser/ui/views/extensions/extension_installed_bubble.cc
+++ b/chrome/browser/ui/views/extensions/extension_installed_bubble.cc
@@ -41,6 +41,8 @@
 #include "ui/views/layout/fill_layout.h"
 #include "ui/views/layout/layout_constants.h"
 
+using extensions::Extension;
+
 namespace {
 
 const int kIconSize = 43;
@@ -387,7 +389,7 @@ void ExtensionInstalledBubble::Observe(
     }
   } else if (type == chrome::NOTIFICATION_EXTENSION_UNLOADED) {
     const Extension* extension =
-        content::Details<UnloadedExtensionInfo>(details)->extension;
+        content::Details<extensions::UnloadedExtensionInfo>(details)->extension;
     if (extension == extension_)
       extension_ = NULL;
   } else {
diff --git a/chrome/browser/ui/views/extensions/extension_installed_bubble.h b/chrome/browser/ui/views/extensions/extension_installed_bubble.h
index 4da3d0e..5cc828d 100644
--- a/chrome/browser/ui/views/extensions/extension_installed_bubble.h
+++ b/chrome/browser/ui/views/extensions/extension_installed_bubble.h
@@ -12,7 +12,10 @@
 #include "ui/views/bubble/bubble_delegate.h"
 
 class Browser;
+
+namespace extensions {
 class Extension;
+}
 
 // Provides feedback to the user upon successful installation of an
 // extension. Depending on the type of extension, the Bubble will
@@ -41,12 +44,13 @@ class ExtensionInstalledBubble
   // the extension has loaded. |extension| is the installed extension. |browser|
   // is the browser window which will host the bubble. |icon| is the install
   // icon of the extension.
-  static void Show(
-      const Extension* extension, Browser *browser, const SkBitmap& icon);
+  static void Show(const extensions::Extension* extension,
+                   Browser *browser,
+                   const SkBitmap& icon);
 
  private:
   // Private ctor. Registers a listener for EXTENSION_LOADED.
-  ExtensionInstalledBubble(const Extension* extension,
+  ExtensionInstalledBubble(const extensions::Extension* extension,
                            Browser *browser,
                            const SkBitmap& icon);
 
@@ -66,7 +70,7 @@ class ExtensionInstalledBubble
   // views::BubbleDelegate
   virtual gfx::Rect GetAnchorRect() OVERRIDE;
 
-  const Extension* extension_;
+  const extensions::Extension* extension_;
   Browser* browser_;
   SkBitmap icon_;
   content::NotificationRegistrar registrar_;
diff --git a/chrome/browser/ui/views/extensions/extension_keybinding_registry_views.cc b/chrome/browser/ui/views/extensions/extension_keybinding_registry_views.cc
index d0a4a48..5a95612 100644
--- a/chrome/browser/ui/views/extensions/extension_keybinding_registry_views.cc
+++ b/chrome/browser/ui/views/extensions/extension_keybinding_registry_views.cc
@@ -27,7 +27,7 @@ ExtensionKeybindingRegistryViews::~ExtensionKeybindingRegistryViews() {
 }
 
 void ExtensionKeybindingRegistryViews::AddExtensionKeybinding(
-    const Extension* extension) {
+    const extensions::Extension* extension) {
   ExtensionCommandService* command_service =
       ExtensionCommandServiceFactory::GetForProfile(profile_);
   // Add all the active keybindings (except page actions and browser actions,
@@ -45,7 +45,7 @@ void ExtensionKeybindingRegistryViews::AddExtensionKeybinding(
 }
 
 void ExtensionKeybindingRegistryViews::RemoveExtensionKeybinding(
-    const Extension* extension) {
+    const extensions::Extension* extension) {
   EventTargets::iterator iter = event_targets_.begin();
   while (iter != event_targets_.end()) {
     if (iter->second.first != extension->id()) {
diff --git a/chrome/browser/ui/views/extensions/extension_keybinding_registry_views.h b/chrome/browser/ui/views/extensions/extension_keybinding_registry_views.h
index f675808..2e83519 100644
--- a/chrome/browser/ui/views/extensions/extension_keybinding_registry_views.h
+++ b/chrome/browser/ui/views/extensions/extension_keybinding_registry_views.h
@@ -13,9 +13,12 @@
 #include "chrome/browser/extensions/extension_keybinding_registry.h"
 #include "ui/base/accelerators/accelerator.h"
 
-class Extension;
 class Profile;
 
+namespace extensions {
+class Extension;
+}
+
 namespace views {
 class FocusManager;
 }
@@ -40,8 +43,10 @@ class ExtensionKeybindingRegistryViews
 
  private:
   // Overridden from ExtensionKeybindingRegistry:
-  virtual void AddExtensionKeybinding(const Extension* extension) OVERRIDE;
-  virtual void RemoveExtensionKeybinding(const Extension* extension) OVERRIDE;
+  virtual void AddExtensionKeybinding(
+      const extensions::Extension* extension) OVERRIDE;
+  virtual void RemoveExtensionKeybinding(
+      const extensions::Extension* extension) OVERRIDE;
 
   // Weak pointer to the our profile. Not owned by us.
   Profile* profile_;
diff --git a/chrome/browser/ui/views/extensions/extension_uninstall_dialog_view.cc b/chrome/browser/ui/views/extensions/extension_uninstall_dialog_view.cc
index bfebd0e..75d0fed 100644
--- a/chrome/browser/ui/views/extensions/extension_uninstall_dialog_view.cc
+++ b/chrome/browser/ui/views/extensions/extension_uninstall_dialog_view.cc
@@ -80,7 +80,7 @@ class ExtensionUninstallDialogDelegateView : public views::DialogDelegateView {
  public:
   ExtensionUninstallDialogDelegateView(
       ExtensionUninstallDialogViews* dialog_view,
-      const Extension* extension,
+      const extensions::Extension* extension,
       SkBitmap* icon);
   virtual ~ExtensionUninstallDialogDelegateView();
 
@@ -156,7 +156,7 @@ void ExtensionUninstallDialogViews::ExtensionUninstallCanceled() {
 
 ExtensionUninstallDialogDelegateView::ExtensionUninstallDialogDelegateView(
     ExtensionUninstallDialogViews* dialog_view,
-    const Extension* extension,
+    const extensions::Extension* extension,
     SkBitmap* icon)
     : dialog_(dialog_view) {
   // Scale down to icon size, but allow smaller icons (don't scale up).
diff --git a/chrome/browser/ui/views/extensions/extension_view.cc b/chrome/browser/ui/views/extensions/extension_view.cc
index a6cdcc7..98592cc 100644
--- a/chrome/browser/ui/views/extensions/extension_view.cc
+++ b/chrome/browser/ui/views/extensions/extension_view.cc
@@ -34,7 +34,7 @@ ExtensionView::~ExtensionView() {
   CleanUp();
 }
 
-const Extension* ExtensionView::extension() const {
+const extensions::Extension* ExtensionView::extension() const {
   return host_->extension();
 }
 
diff --git a/chrome/browser/ui/views/extensions/extension_view.h b/chrome/browser/ui/views/extensions/extension_view.h
index 5254075..37562f7 100644
--- a/chrome/browser/ui/views/extensions/extension_view.h
+++ b/chrome/browser/ui/views/extensions/extension_view.h
@@ -12,10 +12,13 @@
 #include "ui/views/controls/native/native_view_host.h"
 
 class Browser;
-class Extension;
 class ExtensionHost;
 class ExtensionView;
 
+namespace extensions {
+class Extension;
+}
+
 namespace content {
 class RenderViewHost;
 }
@@ -37,7 +40,7 @@ class ExtensionView : public views::NativeViewHost {
 
   ExtensionHost* host() const { return host_; }
   Browser* browser() const { return browser_; }
-  const Extension* extension() const;
+  const extensions::Extension* extension() const;
   content::RenderViewHost* render_view_host() const;
   void DidStopLoading();
   void SetIsClipped(bool is_clipped);
diff --git a/chrome/browser/ui/views/extensions/shell_window_views.cc b/chrome/browser/ui/views/extensions/shell_window_views.cc
index 8ff024b..522c7c6 100644
--- a/chrome/browser/ui/views/extensions/shell_window_views.cc
+++ b/chrome/browser/ui/views/extensions/shell_window_views.cc
@@ -99,7 +99,7 @@ void ShellWindowFrameView::GetWindowMask(const gfx::Size& size,
 }
 
 ShellWindowViews::ShellWindowViews(Profile* profile,
-                                   const Extension* extension,
+                                   const extensions::Extension* extension,
                                    const GURL& url)
     : ShellWindow(profile, extension, url),
       initialized_(false),
@@ -348,7 +348,7 @@ void ShellWindowViews::OnBoundsChanged(const gfx::Rect& previous_bounds) {
 
 // static
 ShellWindow* ShellWindow::CreateImpl(Profile* profile,
-                                     const Extension* extension,
+                                     const extensions::Extension* extension,
                                      const GURL& url) {
   return new ShellWindowViews(profile, extension, url);
 }
diff --git a/chrome/browser/ui/views/extensions/shell_window_views.h b/chrome/browser/ui/views/extensions/shell_window_views.h
index ef35d47..6102ef1 100644
--- a/chrome/browser/ui/views/extensions/shell_window_views.h
+++ b/chrome/browser/ui/views/extensions/shell_window_views.h
@@ -14,12 +14,16 @@
 
 class Profile;
 
+namespace extensions {
+class Extension;
+}
+
 class ShellWindowViews : public ShellWindow,
                          public views::NativeViewHost,
                          public views::WidgetDelegate {
  public:
   ShellWindowViews(Profile* profile,
-                   const Extension* extension,
+                   const extensions::Extension* extension,
                    const GURL& url);
 
   // BaseWindow implementation.
diff --git a/chrome/browser/ui/views/frame/browser_view.cc b/chrome/browser/ui/views/frame/browser_view.cc
index cafd5fb..79846e2 100644
--- a/chrome/browser/ui/views/frame/browser_view.cc
+++ b/chrome/browser/ui/views/frame/browser_view.cc
@@ -1108,8 +1108,9 @@ void BrowserView::ShowCreateWebAppShortcutsDialog(
   browser::ShowCreateWebAppShortcutsDialog(GetNativeHandle(), tab_contents);
 }
 
-void BrowserView::ShowCreateChromeAppShortcutsDialog(Profile* profile,
-                                                     const Extension* app) {
+void BrowserView::ShowCreateChromeAppShortcutsDialog(
+    Profile* profile,
+    const extensions::Extension* app) {
   browser::ShowCreateChromeAppShortcutsDialog(GetNativeHandle(), profile, app);
 }
 
diff --git a/chrome/browser/ui/views/frame/browser_view.h b/chrome/browser/ui/views/frame/browser_view.h
index 8be8d25..27c974a 100644
--- a/chrome/browser/ui/views/frame/browser_view.h
+++ b/chrome/browser/ui/views/frame/browser_view.h
@@ -42,7 +42,6 @@ class Browser;
 class BrowserViewLayout;
 class ContentsContainer;
 class DownloadShelfView;
-class Extension;
 class FullscreenExitBubbleViews;
 class InfoBarContainerView;
 class LocationBarView;
@@ -59,6 +58,10 @@ class JumpList;
 class BrowserLauncherItemController;
 #endif
 
+namespace extensions {
+class Extension;
+}
+
 namespace views {
 class AccessiblePaneView;
 class ExternalFocusTracker;
@@ -302,7 +305,7 @@ class BrowserView : public BrowserWindow,
   virtual void ShowCreateWebAppShortcutsDialog(
       TabContentsWrapper* tab_contents) OVERRIDE;
   virtual void ShowCreateChromeAppShortcutsDialog(
-      Profile*, const Extension* app) OVERRIDE;
+      Profile*, const extensions::Extension* app) OVERRIDE;
   virtual void Cut() OVERRIDE;
   virtual void Copy() OVERRIDE;
   virtual void Paste() OVERRIDE;
diff --git a/chrome/browser/ui/views/infobars/extension_infobar.cc b/chrome/browser/ui/views/infobars/extension_infobar.cc
index 43cb151..646ec46 100644
--- a/chrome/browser/ui/views/infobars/extension_infobar.cc
+++ b/chrome/browser/ui/views/infobars/extension_infobar.cc
@@ -90,7 +90,7 @@ void ExtensionInfoBar::ViewHierarchyChanged(bool is_add,
   // This must happen after adding all children because it can trigger layout,
   // which assumes that particular children (e.g. the close button) have already
   // been added.
-  const Extension* extension = extension_host->extension();
+  const extensions::Extension* extension = extension_host->extension();
   ExtensionIconSet::Icons image_size = ExtensionIconSet::EXTENSION_ICON_BITTY;
   ExtensionResource icon_resource = extension->GetIconResource(
       image_size, ExtensionIconSet::MATCH_EXACTLY);
@@ -142,7 +142,8 @@ void ExtensionInfoBar::OnMenuButtonClicked(views::View* source,
                                            const gfx::Point& point) {
   if (!owned())
     return;  // We're closing; don't call anything, it might access the owner.
-  const Extension* extension = GetDelegate()->extension_host()->extension();
+  const extensions::Extension* extension = GetDelegate()->extension_host()->
+      extension();
   if (!extension->ShowConfigureContextMenus())
     return;
 
diff --git a/chrome/browser/ui/views/location_bar/page_action_image_view.cc b/chrome/browser/ui/views/location_bar/page_action_image_view.cc
index a7bcf21a..43a1db9 100644
--- a/chrome/browser/ui/views/location_bar/page_action_image_view.cc
+++ b/chrome/browser/ui/views/location_bar/page_action_image_view.cc
@@ -29,6 +29,7 @@
 #include "ui/views/controls/menu/menu_runner.h"
 
 using content::WebContents;
+using extensions::Extension;
 
 PageActionImageView::PageActionImageView(LocationBarView* owner,
                                          ExtensionAction* page_action,
@@ -272,7 +273,7 @@ void PageActionImageView::Observe(int type,
                                   const content::NotificationDetails& details) {
   DCHECK_EQ(chrome::NOTIFICATION_EXTENSION_UNLOADED, type);
   const Extension* unloaded_extension =
-      content::Details<UnloadedExtensionInfo>(details)->extension;
+      content::Details<extensions::UnloadedExtensionInfo>(details)->extension;
   if (page_action_ == unloaded_extension ->page_action())
     owner_->UpdatePageActions();
 }
diff --git a/chrome/browser/ui/views/location_bar/page_action_with_badge_view.cc b/chrome/browser/ui/views/location_bar/page_action_with_badge_view.cc
index 569ea44..821119a 100644
--- a/chrome/browser/ui/views/location_bar/page_action_with_badge_view.cc
+++ b/chrome/browser/ui/views/location_bar/page_action_with_badge_view.cc
@@ -22,8 +22,8 @@ void PageActionWithBadgeView::GetAccessibleState(
 }
 
 gfx::Size PageActionWithBadgeView::GetPreferredSize() {
-  return gfx::Size(Extension::kPageActionIconMaxSize,
-                   Extension::kPageActionIconMaxSize);
+  return gfx::Size(extensions::Extension::kPageActionIconMaxSize,
+                   extensions::Extension::kPageActionIconMaxSize);
 }
 
 void PageActionWithBadgeView::Layout() {
diff --git a/chrome/browser/ui/webui/extensions/extension_activity_ui.cc b/chrome/browser/ui/webui/extensions/extension_activity_ui.cc
index 155cf4a..90996d9 100644
--- a/chrome/browser/ui/webui/extensions/extension_activity_ui.cc
+++ b/chrome/browser/ui/webui/extensions/extension_activity_ui.cc
@@ -90,7 +90,7 @@ void ExtensionActivityUI::HandleRequestExtensionData(
 }
 
 void ExtensionActivityUI::OnExtensionActivity(
-      const Extension* extension,
+      const extensions::Extension* extension,
       ExtensionActivityLog::Activity activity,
       const std::string& msg) {
   DictionaryValue result;
diff --git a/chrome/browser/ui/webui/extensions/extension_activity_ui.h b/chrome/browser/ui/webui/extensions/extension_activity_ui.h
index 54728ed..abcdcbc 100644
--- a/chrome/browser/ui/webui/extensions/extension_activity_ui.h
+++ b/chrome/browser/ui/webui/extensions/extension_activity_ui.h
@@ -9,6 +9,10 @@
 #include "chrome/browser/extensions/extension_activity_log.h"
 #include "content/public/browser/web_ui_controller.h"
 
+namespace extensions {
+class Extension;
+}
+
 class ExtensionActivityUI : public content::WebUIController,
                             public ExtensionActivityLog::Observer {
  public:
@@ -19,12 +23,12 @@ class ExtensionActivityUI : public content::WebUIController,
   void HandleRequestExtensionData(const base::ListValue* args);
 
   // ExtensionActivityLog::Observer implementation.
-  virtual void OnExtensionActivity(const Extension* extension,
+  virtual void OnExtensionActivity(const extensions::Extension* extension,
                                    ExtensionActivityLog::Activity activity,
                                    const std::string& msg) OVERRIDE;
 
  private:
-  const Extension* extension_;
+  const extensions::Extension* extension_;
 
   DISALLOW_COPY_AND_ASSIGN(ExtensionActivityUI);
 };
diff --git a/chrome/browser/ui/webui/extensions/extension_icon_source.cc b/chrome/browser/ui/webui/extensions/extension_icon_source.cc
index a8bbec6..850db95 100644
--- a/chrome/browser/ui/webui/extensions/extension_icon_source.cc
+++ b/chrome/browser/ui/webui/extensions/extension_icon_source.cc
@@ -60,14 +60,14 @@ ExtensionIconSource::ExtensionIconSource(Profile* profile)
 
 struct ExtensionIconSource::ExtensionIconRequest {
   int request_id;
-  const Extension* extension;
+  const extensions::Extension* extension;
   bool grayscale;
   int size;
   ExtensionIconSet::MatchType match;
 };
 
 // static
-GURL ExtensionIconSource::GetIconURL(const Extension* extension,
+GURL ExtensionIconSource::GetIconURL(const extensions::Extension* extension,
                                      int icon_size,
                                      ExtensionIconSet::MatchType match,
                                      bool grayscale,
@@ -296,7 +296,7 @@ bool ExtensionIconSource::ParseData(const std::string& path,
     match_type = ExtensionIconSet::MATCH_EXACTLY;
 
   std::string extension_id = path_parts.at(0);
-  const Extension* extension =
+  const extensions::Extension* extension =
       profile_->GetExtensionService()->GetInstalledExtension(extension_id);
   if (!extension)
     return false;
@@ -316,7 +316,7 @@ void ExtensionIconSource::SendDefaultResponse(int request_id) {
 }
 
 void ExtensionIconSource::SetData(int request_id,
-                                  const Extension* extension,
+                                  const extensions::Extension* extension,
                                   bool grayscale,
                                   int size,
                                   ExtensionIconSet::MatchType match) {
diff --git a/chrome/browser/ui/webui/extensions/extension_icon_source.h b/chrome/browser/ui/webui/extensions/extension_icon_source.h
index 8cf5827..4195137 100644
--- a/chrome/browser/ui/webui/extensions/extension_icon_source.h
+++ b/chrome/browser/ui/webui/extensions/extension_icon_source.h
@@ -19,6 +19,10 @@
 class ExtensionIconSet;
 class Profile;
 
+namespace extensions {
+class Extension;
+}
+
 // ExtensionIconSource serves extension icons through network level chrome:
 // requests. Icons can be retrieved for any installed extension or app.
 //
@@ -55,7 +59,7 @@ class ExtensionIconSource : public ChromeURLDataManager::DataSource,
   // desaturated version of the icon. |exists|, if non-NULL, will be set to true
   // if the icon exists; false if it will lead to a default or not-present
   // image.
-  static GURL GetIconURL(const Extension* extension,
+  static GURL GetIconURL(const extensions::Extension* extension,
                          int icon_size,
                          ExtensionIconSet::MatchType match,
                          bool grayscale,
@@ -131,7 +135,7 @@ class ExtensionIconSource : public ChromeURLDataManager::DataSource,
   // Stores the parameters associated with the |request_id|, making them
   // as an ExtensionIconRequest via GetData.
   void SetData(int request_id,
-               const Extension* extension,
+               const extensions::Extension* extension,
                bool grayscale,
                int size,
                ExtensionIconSet::MatchType match);
diff --git a/chrome/browser/ui/webui/extensions/extension_settings_handler.cc b/chrome/browser/ui/webui/extensions/extension_settings_handler.cc
index 3993240..6294f94 100644
--- a/chrome/browser/ui/webui/extensions/extension_settings_handler.cc
+++ b/chrome/browser/ui/webui/extensions/extension_settings_handler.cc
@@ -54,6 +54,7 @@
 
 using content::RenderViewHost;
 using content::WebContents;
+using extensions::Extension;
 using extensions::ExtensionUpdater;
 
 ///////////////////////////////////////////////////////////////////////////////
diff --git a/chrome/browser/ui/webui/extensions/extension_settings_handler.h b/chrome/browser/ui/webui/extensions/extension_settings_handler.h
index fb22192..ff6804c 100644
--- a/chrome/browser/ui/webui/extensions/extension_settings_handler.h
+++ b/chrome/browser/ui/webui/extensions/extension_settings_handler.h
@@ -25,7 +25,6 @@
 #include "content/public/browser/web_ui_message_handler.h"
 #include "googleurl/src/gurl.h"
 
-class Extension;
 class ExtensionHost;
 class ExtensionService;
 class FilePath;
@@ -36,6 +35,10 @@ class DictionaryValue;
 class ListValue;
 }
 
+namespace extensions {
+class Extension;
+}
+
 // Information about a page running in an extension, for example a popup bubble,
 // a background page, or a tab contents.
 struct ExtensionPage {
@@ -67,7 +70,7 @@ class ExtensionSettingsHandler : public content::WebUIMessageHandler,
   // testing.
   // Note: |warning_set| can be NULL in unit tests.
   base::DictionaryValue* CreateExtensionDetailValue(
-      const Extension* extension,
+      const extensions::Extension* extension,
       const std::vector<ExtensionPage>& pages,
       const ExtensionWarningSet* warning_set);
 
@@ -144,7 +147,7 @@ class ExtensionSettingsHandler : public content::WebUIMessageHandler,
 
   // Utility for callbacks that get an extension ID as the sole argument.
   // Returns NULL if the extension isn't active.
-  const Extension* GetActiveExtension(const base::ListValue* args);
+  const extensions::Extension* GetActiveExtension(const base::ListValue* args);
 
   // Forces a UI update if appropriate after a notification is received.
   void MaybeUpdateAfterNotification();
@@ -154,7 +157,7 @@ class ExtensionSettingsHandler : public content::WebUIMessageHandler,
 
   // Helper that lists the current inspectable html pages for an extension.
   std::vector<ExtensionPage> GetInspectablePagesForExtension(
-      const Extension* extension, bool extension_is_enabled);
+      const extensions::Extension* extension, bool extension_is_enabled);
   void GetInspectablePagesForExtensionProcess(
       const std::set<content::RenderViewHost*>& views,
       std::vector<ExtensionPage> *result);
diff --git a/chrome/browser/ui/webui/inspect_ui.cc b/chrome/browser/ui/webui/inspect_ui.cc
index a5a0194..482aa86 100644
--- a/chrome/browser/ui/webui/inspect_ui.cc
+++ b/chrome/browser/ui/webui/inspect_ui.cc
@@ -132,8 +132,8 @@ DictionaryValue* BuildTargetDescriptor(RenderViewHost* rvh, bool is_tab) {
         web_contents->GetBrowserContext());
     if (profile) {
       ExtensionService* extension_service = profile->GetExtensionService();
-      const Extension* extension = extension_service->extensions()->GetByID(
-          web_contents->GetURL().host());
+      const extensions::Extension* extension = extension_service->
+          extensions()->GetByID(web_contents->GetURL().host());
       if (extension) {
         target_type = kExtensionTargetType;
         title = extension->name();
diff --git a/chrome/browser/ui/webui/ntp/app_launcher_handler.cc b/chrome/browser/ui/webui/ntp/app_launcher_handler.cc
index e56bcef..9963f23 100644
--- a/chrome/browser/ui/webui/ntp/app_launcher_handler.cc
+++ b/chrome/browser/ui/webui/ntp/app_launcher_handler.cc
@@ -52,6 +52,7 @@
 #include "ui/gfx/codec/png_codec.h"
 
 using content::WebContents;
+using extensions::Extension;
 
 namespace {
 
@@ -273,15 +274,16 @@ void AppLauncherHandler::Observe(int type,
     }
     case chrome::NOTIFICATION_EXTENSION_UNLOADED: {
       const Extension* extension =
-          content::Details<UnloadedExtensionInfo>(details)->extension;
+          content::Details<extensions::UnloadedExtensionInfo>(
+              details)->extension;
       if (!extension->is_app())
         return;
 
       scoped_ptr<DictionaryValue> app_info(GetAppInfo(extension));
       scoped_ptr<base::FundamentalValue> uninstall_value(
           Value::CreateBooleanValue(
-              content::Details<UnloadedExtensionInfo>(details)->reason ==
-              extension_misc::UNLOAD_REASON_UNINSTALL));
+              content::Details<extensions::UnloadedExtensionInfo>(
+                  details)->reason == extension_misc::UNLOAD_REASON_UNINSTALL));
       if (app_info.get()) {
         scoped_ptr<base::FundamentalValue> from_page(
             Value::CreateBooleanValue(!extension_id_prompting_.empty()));
@@ -982,8 +984,8 @@ ExtensionInstallUI* AppLauncherHandler::GetExtensionInstallUI() {
 
 void AppLauncherHandler::UninstallDefaultApps() {
   AppsPromo* apps_promo = extension_service_->apps_promo();
-  const ExtensionIdSet& app_ids = apps_promo->old_default_apps();
-  for (ExtensionIdSet::const_iterator iter = app_ids.begin();
+  const extensions::ExtensionIdSet& app_ids = apps_promo->old_default_apps();
+  for (extensions::ExtensionIdSet::const_iterator iter = app_ids.begin();
        iter != app_ids.end(); ++iter) {
     if (extension_service_->GetExtensionById(*iter, true))
       extension_service_->UninstallExtension(*iter, false, NULL);
diff --git a/chrome/browser/ui/webui/ntp/app_launcher_handler.h b/chrome/browser/ui/webui/ntp/app_launcher_handler.h
index 66a731f..88494c5 100644
--- a/chrome/browser/ui/webui/ntp/app_launcher_handler.h
+++ b/chrome/browser/ui/webui/ntp/app_launcher_handler.h
@@ -37,7 +37,7 @@ class AppLauncherHandler : public content::WebUIMessageHandler,
 
   // Populate a dictionary with the information from an extension.
   static void CreateAppInfo(
-      const Extension* extension,
+      const extensions::Extension* extension,
       const AppNotification* notification,
       ExtensionService* service,
       base::DictionaryValue* value);
@@ -56,7 +56,7 @@ class AppLauncherHandler : public content::WebUIMessageHandler,
   // Create a dictionary value for the given extension. May return NULL, e.g. if
   // the given extension is not an app. If non-NULL, the caller assumes
   // ownership of the pointer.
-  base::DictionaryValue* GetAppInfo(const Extension* extension);
+  base::DictionaryValue* GetAppInfo(const extensions::Extension* extension);
 
   // Populate the given dictionary with the web store promo content.
   void FillPromoDictionary(base::DictionaryValue* value);
diff --git a/chrome/browser/ui/webui/ntp/favicon_webui_handler.cc b/chrome/browser/ui/webui/ntp/favicon_webui_handler.cc
index 7286db9..1002ddd 100644
--- a/chrome/browser/ui/webui/ntp/favicon_webui_handler.cc
+++ b/chrome/browser/ui/webui/ntp/favicon_webui_handler.cc
@@ -142,7 +142,7 @@ void FaviconWebUIHandler::HandleGetAppIconDominantColor(
 
   ExtensionService* extension_service =
       Profile::FromWebUI(web_ui())->GetExtensionService();
-  const Extension* extension = extension_service->GetExtensionById(
+  const extensions::Extension* extension = extension_service->GetExtensionById(
       extension_id, false);
   if (!extension)
     return;
diff --git a/chrome/browser/ui/webui/options2/search_engine_manager_handler2.cc b/chrome/browser/ui/webui/options2/search_engine_manager_handler2.cc
index 38f03a3..02fffb5 100644
--- a/chrome/browser/ui/webui/options2/search_engine_manager_handler2.cc
+++ b/chrome/browser/ui/webui/options2/search_engine_manager_handler2.cc
@@ -166,7 +166,7 @@ void SearchEngineManagerHandler::OnItemsRemoved(int start, int length) {
 }
 
 base::DictionaryValue* SearchEngineManagerHandler::CreateDictionaryForExtension(
-    const Extension& extension) {
+    const extensions::Extension& extension) {
   base::DictionaryValue* dict = new base::DictionaryValue();
   dict->SetString("name",  extension.name());
   dict->SetString("displayName", extension.name());
diff --git a/chrome/browser/ui/webui/options2/search_engine_manager_handler2.h b/chrome/browser/ui/webui/options2/search_engine_manager_handler2.h
index 95af05ed..e2bddaf 100644
--- a/chrome/browser/ui/webui/options2/search_engine_manager_handler2.h
+++ b/chrome/browser/ui/webui/options2/search_engine_manager_handler2.h
@@ -9,9 +9,12 @@
 #include "chrome/browser/ui/webui/options2/options_ui2.h"
 #include "ui/base/models/table_model_observer.h"
 
-class Extension;
 class KeywordEditorController;
 
+namespace extensions {
+class Extension;
+}
+
 namespace options2 {
 
 class SearchEngineManagerHandler : public OptionsPageUIHandler,
@@ -73,7 +76,7 @@ class SearchEngineManagerHandler : public OptionsPageUIHandler,
 
   // Returns a dictionary to pass to WebUI representing the extension.
   base::DictionaryValue* CreateDictionaryForExtension(
-      const Extension& extension);
+      const extensions::Extension& extension);
 
   DISALLOW_COPY_AND_ASSIGN(SearchEngineManagerHandler);
 };
diff --git a/chrome/browser/ui/webui/uber/uber_ui.cc b/chrome/browser/ui/webui/uber/uber_ui.cc
index ae431a9..c671115 100644
--- a/chrome/browser/ui/webui/uber/uber_ui.cc
+++ b/chrome/browser/ui/webui/uber/uber_ui.cc
@@ -72,8 +72,9 @@ bool HasExtensionType(Profile* profile, const char* extensionType) {
 
   for (ExtensionSet::const_iterator iter = extensionSet->begin();
        iter != extensionSet->end(); ++iter) {
-    Extension::URLOverrideMap map = (*iter)->GetChromeURLOverrides();
-    Extension::URLOverrideMap::const_iterator result =
+    extensions::Extension::URLOverrideMap map =
+        (*iter)->GetChromeURLOverrides();
+    extensions::Extension::URLOverrideMap::const_iterator result =
         map.find(std::string(extensionType));
 
     if (result != map.end())
diff --git a/chrome/browser/web_applications/web_app.cc b/chrome/browser/web_applications/web_app.cc
index cc58900..a502b5a 100644
--- a/chrome/browser/web_applications/web_app.cc
+++ b/chrome/browser/web_applications/web_app.cc
@@ -81,7 +81,7 @@ FilePath GetWebAppDataDirectory(const FilePath& profile_path,
 }
 
 FilePath GetWebAppDataDirectory(const FilePath& profile_path,
-                                const Extension& extension) {
+                                const extensions::Extension& extension) {
   return GetWebAppDataDirectory(
       profile_path, extension.id(), GURL(extension.launch_web_url()));
 }
diff --git a/chrome/browser/web_applications/web_app.h b/chrome/browser/web_applications/web_app.h
index a9e55a6..253c88f 100644
--- a/chrome/browser/web_applications/web_app.h
+++ b/chrome/browser/web_applications/web_app.h
@@ -14,7 +14,9 @@
 #include "chrome/browser/shell_integration.h"
 #include "chrome/common/web_apps.h"
 
+namespace extensions {
 class Extension;
+}
 
 namespace web_app {
 
@@ -28,7 +30,7 @@ FilePath GetWebAppDataDirectory(const FilePath& profile_path,
 // Gets the user data directory to use for |extension| located inside
 // |profile_path|.
 FilePath GetWebAppDataDirectory(const FilePath& profile_path,
-                                const Extension& extension);
+                                const extensions::Extension& extension);
 
 // Compute a deterministic name based on data in the shortcut_info.
 std::string GenerateApplicationNameFromInfo(
diff --git a/chrome/common/extensions/api/extension_api.h b/chrome/common/extensions/api/extension_api.h
index cbbdaad..9cfba19 100644
--- a/chrome/common/extensions/api/extension_api.h
+++ b/chrome/common/extensions/api/extension_api.h
@@ -27,11 +27,11 @@ class Value;
 }
 
 class GURL;
-class Extension;
 class ExtensionPermissionSet;
 
 namespace extensions {
 
+class Extension;
 class Feature;
 
 // C++ Wrapper for the JSON API definitions in chrome/common/extensions/api/.
diff --git a/chrome/common/extensions/extension.cc b/chrome/common/extensions/extension.cc
index 0c88438..539e238 100644
--- a/chrome/common/extensions/extension.cc
+++ b/chrome/common/extensions/extension.cc
@@ -59,6 +59,8 @@ namespace switch_utils = extensions::switch_utils;
 using extensions::csp_validator::ContentSecurityPolicyIsLegal;
 using extensions::csp_validator::ContentSecurityPolicyIsSecure;
 
+namespace extensions {
+
 namespace {
 
 const int kModernManifestVersion = 1;
@@ -3560,3 +3562,5 @@ UpdatedExtensionPermissionsInfo::UpdatedExtensionPermissionsInfo(
     : reason(reason),
       extension(extension),
       permissions(permissions) {}
+
+}   // namespace extensions
diff --git a/chrome/common/extensions/extension.h b/chrome/common/extensions/extension.h
index 5e7df6f..2e68ab1 100644
--- a/chrome/common/extensions/extension.h
+++ b/chrome/common/extensions/extension.h
@@ -42,14 +42,16 @@ class DictionaryValue;
 class ListValue;
 }
 
-namespace extensions {
-class Manifest;
-}
-
 namespace webkit_glue {
 struct WebIntentServiceData;
 }
 
+FORWARD_DECLARE_TEST(TabStripModelTest, Apps);
+
+namespace extensions {
+
+class Manifest;
+
 // Represents a Chrome extension.
 class Extension : public base::RefCountedThreadSafe<Extension> {
  public:
@@ -1062,7 +1064,7 @@ class Extension : public base::RefCountedThreadSafe<Extension> {
   std::string content_security_policy_;
 
   FRIEND_TEST_ALL_PREFIXES(ExtensionTest, LoadPageActionHelper);
-  FRIEND_TEST_ALL_PREFIXES(TabStripModelTest, Apps);
+  FRIEND_TEST_ALL_PREFIXES(::TabStripModelTest, Apps);
 
   DISALLOW_COPY_AND_ASSIGN(Extension);
 };
@@ -1124,4 +1126,6 @@ struct UpdatedExtensionPermissionsInfo {
       Reason reason);
 };
 
+} // namespace extensions
+
 #endif  // CHROME_COMMON_EXTENSIONS_EXTENSION_H_
diff --git a/chrome/common/extensions/extension_file_util.cc b/chrome/common/extensions/extension_file_util.cc
index 848625e..ec72db7 100644
--- a/chrome/common/extensions/extension_file_util.cc
+++ b/chrome/common/extensions/extension_file_util.cc
@@ -29,12 +29,15 @@
 #include "net/base/file_stream.h"
 #include "ui/base/l10n/l10n_util.h"
 
+using extensions::Extension;
+
 namespace errors = extension_manifest_errors;
 
 namespace extension_file_util {
 
 // Validates locale info. Doesn't check if messages.json files are valid.
-static bool ValidateLocaleInfo(const Extension& extension, std::string* error);
+static bool ValidateLocaleInfo(const Extension& extension,
+                               std::string* error);
 
 // Returns false and sets the error if script file can't be loaded,
 // or if it's not UTF-8 encoded.
@@ -124,8 +127,7 @@ scoped_refptr<Extension> LoadExtension(const FilePath& extension_path,
                                        Extension::Location location,
                                        int flags,
                                        std::string* error) {
-  return LoadExtension(
-      extension_path, std::string(), location, flags, error);
+  return LoadExtension(extension_path, std::string(), location, flags, error);
 }
 
 scoped_refptr<Extension> LoadExtension(const FilePath& extension_path,
@@ -140,13 +142,12 @@ scoped_refptr<Extension> LoadExtension(const FilePath& extension_path,
                                               error))
     return NULL;
 
-  scoped_refptr<Extension> extension(Extension::Create(
-      extension_path,
-      location,
-      *manifest,
-      flags,
-      extension_id,
-      error));
+  scoped_refptr<Extension> extension(Extension::Create(extension_path,
+                                                       location,
+                                                       *manifest,
+                                                       flags,
+                                                       extension_id,
+                                                       error));
   if (!extension.get())
     return NULL;
 
@@ -190,7 +191,8 @@ DictionaryValue* LoadManifest(const FilePath& extension_path,
   return static_cast<DictionaryValue*>(root.release());
 }
 
-bool ValidateExtension(const Extension* extension, std::string* error) {
+bool ValidateExtension(const Extension* extension,
+                       std::string* error) {
   // Validate icons exist.
   for (ExtensionIconSet::IconMap::const_iterator iter =
            extension->icons().map().begin();
@@ -435,7 +437,8 @@ ExtensionMessageBundle* LoadExtensionMessageBundle(
     std::string* error) {
   error->clear();
   // Load locale information if available.
-  FilePath locale_path = extension_path.Append(Extension::kLocaleFolder);
+  FilePath locale_path = extension_path.Append(
+      Extension::kLocaleFolder);
   if (!file_util::PathExists(locale_path))
     return NULL;
 
@@ -484,9 +487,11 @@ SubstitutionMap* LoadExtensionMessageBundleSubstitutionMap(
   return returnValue;
 }
 
-static bool ValidateLocaleInfo(const Extension& extension, std::string* error) {
+static bool ValidateLocaleInfo(const Extension& extension,
+                               std::string* error) {
   // default_locale and _locales have to be both present or both missing.
-  const FilePath path = extension.path().Append(Extension::kLocaleFolder);
+  const FilePath path = extension.path().Append(
+      Extension::kLocaleFolder);
   bool path_exists = file_util::PathExists(path);
   std::string default_locale = extension.default_locale();
 
diff --git a/chrome/common/extensions/extension_file_util.h b/chrome/common/extensions/extension_file_util.h
index 1ad1120..96f38fb 100644
--- a/chrome/common/extensions/extension_file_util.h
+++ b/chrome/common/extensions/extension_file_util.h
@@ -12,7 +12,6 @@
 #include "chrome/common/extensions/extension.h"
 #include "chrome/common/extensions/extension_message_bundle.h"
 
-class Extension;
 class ExtensionMessageBundle;
 class FilePath;
 class GURL;
@@ -41,17 +40,19 @@ void UninstallExtension(const FilePath& extensions_dir,
 
 // Loads and validates an extension from the specified directory. Returns NULL
 // on failure, with a description of the error in |error|.
-scoped_refptr<Extension> LoadExtension(const FilePath& extension_root,
-                                       Extension::Location location,
-                                       int flags,
-                                       std::string* error);
+scoped_refptr<extensions::Extension> LoadExtension(
+    const FilePath& extension_root,
+    extensions::Extension::Location location,
+    int flags,
+    std::string* error);
 
 // The same as LoadExtension except use the provided |extension_id|.
-scoped_refptr<Extension> LoadExtension(const FilePath& extension_root,
-                                       const std::string& extension_id,
-                                       Extension::Location location,
-                                       int flags,
-                                       std::string* error);
+scoped_refptr<extensions::Extension> LoadExtension(
+    const FilePath& extension_root,
+    const std::string& extension_id,
+    extensions::Extension::Location location,
+    int flags,
+    std::string* error);
 
 // Loads an extension manifest from the specified directory. Returns NULL
 // on failure, with a description of the error in |error|.
@@ -60,7 +61,8 @@ base::DictionaryValue* LoadManifest(const FilePath& extension_root,
 
 // Returns true if the given extension object is valid and consistent.
 // Otherwise, a description of the error is returned in |error|.
-bool ValidateExtension(const Extension* extension, std::string* error);
+bool ValidateExtension(const extensions::Extension* extension,
+                       std::string* error);
 
 // Cleans up the extension install directory. It can end up with garbage in it
 // if extensions can't initially be removed when they are uninstalled (eg if a
diff --git a/chrome/common/extensions/extension_file_util_unittest.cc b/chrome/common/extensions/extension_file_util_unittest.cc
index eef0a63..04d8b91 100644
--- a/chrome/common/extensions/extension_file_util_unittest.cc
+++ b/chrome/common/extensions/extension_file_util_unittest.cc
@@ -17,6 +17,8 @@
 #include "testing/gtest/include/gtest/gtest.h"
 #include "ui/base/l10n/l10n_util.h"
 
+using extensions::Extension;
+
 namespace keys = extension_manifest_keys;
 
 #if defined(OS_WIN)
diff --git a/chrome/common/extensions/extension_l10n_util.cc b/chrome/common/extensions/extension_l10n_util.cc
index 117ac74..1fa88e7 100644
--- a/chrome/common/extensions/extension_l10n_util.cc
+++ b/chrome/common/extensions/extension_l10n_util.cc
@@ -48,7 +48,7 @@ std::string GetDefaultLocaleFromManifest(const DictionaryValue& manifest,
 
 }
 
-bool ShouldRelocalizeManifest(const ExtensionInfo& info) {
+bool ShouldRelocalizeManifest(const extensions::ExtensionInfo& info) {
   DictionaryValue* manifest = info.extension_manifest.get();
   if (!manifest)
     return false;
@@ -206,7 +206,7 @@ bool AddLocale(const std::set<std::string>& chrome_locales,
   }
   // Check if messages file is actually present (but don't check content).
   if (file_util::PathExists(
-      locale_folder.Append(Extension::kMessagesFilename))) {
+      locale_folder.Append(extensions::Extension::kMessagesFilename))) {
     valid_locales->insert(locale_name);
   } else {
     *error = base::StringPrintf("Catalog file is missing for locale %s.",
@@ -279,7 +279,7 @@ static DictionaryValue* LoadMessageFile(const FilePath& locale_path,
                                         std::string* error) {
   std::string extension_locale = locale;
   FilePath file = locale_path.AppendASCII(extension_locale)
-      .Append(Extension::kMessagesFilename);
+      .Append(extensions::Extension::kMessagesFilename);
   JSONFileValueSerializer messages_serializer(file);
   Value *dictionary = messages_serializer.Deserialize(NULL, error);
   if (!dictionary && error->empty()) {
diff --git a/chrome/common/extensions/extension_l10n_util.h b/chrome/common/extensions/extension_l10n_util.h
index 8b08e4a..e96a858 100644
--- a/chrome/common/extensions/extension_l10n_util.h
+++ b/chrome/common/extensions/extension_l10n_util.h
@@ -12,15 +12,17 @@
 #include <string>
 #include <vector>
 
-class Extension;
 class ExtensionMessageBundle;
 class FilePath;
-struct ExtensionInfo;
 
 namespace base {
 class DictionaryValue;
 }
 
+namespace extensions {
+struct ExtensionInfo;
+}
+
 namespace extension_l10n_util {
 
 // Set the locale for this process to a fixed value, rather than using the
@@ -35,7 +37,7 @@ std::string GetDefaultLocaleFromManifest(const base::DictionaryValue& manifest,
 
 // Returns true iff the extension was localized, and the current locale
 // doesn't match the locale written into info.extension_manifest.
-bool ShouldRelocalizeManifest(const ExtensionInfo& info);
+bool ShouldRelocalizeManifest(const extensions::ExtensionInfo& info);
 
 // Localize extension name, description, browser_action and other fields
 // in the manifest.
diff --git a/chrome/common/extensions/extension_l10n_util_unittest.cc b/chrome/common/extensions/extension_l10n_util_unittest.cc
index 182875e..5e0b46a 100644
--- a/chrome/common/extensions/extension_l10n_util_unittest.cc
+++ b/chrome/common/extensions/extension_l10n_util_unittest.cc
@@ -17,6 +17,9 @@
 #include "testing/gtest/include/gtest/gtest.h"
 #include "ui/base/l10n/l10n_util.h"
 
+using extensions::Extension;
+using extensions::ExtensionInfo;
+
 namespace errors = extension_manifest_errors;
 namespace keys = extension_manifest_keys;
 
diff --git a/chrome/common/extensions/extension_messages.cc b/chrome/common/extensions/extension_messages.cc
index 838943d..db167d1 100644
--- a/chrome/common/extensions/extension_messages.cc
+++ b/chrome/common/extensions/extension_messages.cc
@@ -4,10 +4,13 @@
 
 #include "chrome/common/extensions/extension_messages.h"
 
+#include "chrome/common/extensions/extension.h"
 #include "chrome/common/extensions/extension_constants.h"
 #include "chrome/common/extensions/manifest.h"
 #include "content/public/common/common_param_traits.h"
 
+using extensions::Extension;
+
 ExtensionMsg_Loaded_Params::ExtensionMsg_Loaded_Params()
     : location(Extension::INVALID),
       creation_flags(Extension::NO_FLAGS){}
diff --git a/chrome/common/extensions/extension_messages.h b/chrome/common/extensions/extension_messages.h
index 4b634a6..0c40ec9 100644
--- a/chrome/common/extensions/extension_messages.h
+++ b/chrome/common/extensions/extension_messages.h
@@ -103,16 +103,16 @@ typedef std::map<std::string, std::string> SubstitutionMap;
 struct ExtensionMsg_Loaded_Params {
   ExtensionMsg_Loaded_Params();
   ~ExtensionMsg_Loaded_Params();
-  explicit ExtensionMsg_Loaded_Params(const Extension* extension);
+  explicit ExtensionMsg_Loaded_Params(const extensions::Extension* extension);
 
   // Creates a new extension from the data in this object.
-  scoped_refptr<Extension> ConvertToExtension() const;
+  scoped_refptr<extensions::Extension> ConvertToExtension() const;
 
   // The subset of the extension manifest data we send to renderers.
   linked_ptr<DictionaryValue> manifest;
 
   // The location the extension was installed from.
-  Extension::Location location;
+  extensions::Extension::Location location;
 
   // The path the extension was loaded from. This is used in the renderer only
   // to generate the extension ID for extensions that are loaded unpacked.
@@ -214,7 +214,8 @@ IPC_MESSAGE_CONTROL1(ExtensionMsg_Unloaded,
 // Updates the scripting whitelist for extensions in the render process. This is
 // only used for testing.
 IPC_MESSAGE_CONTROL1(ExtensionMsg_SetScriptingWhitelist,
-                     Extension::ScriptingWhitelist /* extenison ids */)
+                     // extension ids
+                     extensions::Extension::ScriptingWhitelist)
 
 // Notification that renderer should run some JavaScript code.
 IPC_MESSAGE_ROUTED1(ExtensionMsg_ExecuteCode,
diff --git a/chrome/common/extensions/extension_permission_set.cc b/chrome/common/extensions/extension_permission_set.cc
index d1d5b55..c456146 100644
--- a/chrome/common/extensions/extension_permission_set.cc
+++ b/chrome/common/extensions/extension_permission_set.cc
@@ -452,7 +452,7 @@ ExtensionAPIPermission* ExtensionPermissionsInfo::RegisterPermission(
 ExtensionPermissionSet::ExtensionPermissionSet() {}
 
 ExtensionPermissionSet::ExtensionPermissionSet(
-    const Extension* extension,
+    const extensions::Extension* extension,
     const ExtensionAPIPermissionSet& apis,
     const URLPatternSet& explicit_hosts,
     const ExtensionOAuth2Scopes& scopes)
@@ -869,7 +869,7 @@ std::set<std::string> ExtensionPermissionSet::GetDistinctHosts(
 }
 
 void ExtensionPermissionSet::InitImplicitExtensionPermissions(
-    const Extension* extension) {
+    const extensions::Extension* extension) {
   // Add the implied permissions.
   if (!extension->plugins().empty())
     apis_.insert(ExtensionAPIPermission::kPlugin);
diff --git a/chrome/common/extensions/extension_permission_set.h b/chrome/common/extensions/extension_permission_set.h
index a0165e4..02011a0 100644
--- a/chrome/common/extensions/extension_permission_set.h
+++ b/chrome/common/extensions/extension_permission_set.h
@@ -19,9 +19,12 @@
 
 // TODO(jstritar): Move each class to its own file in extensions/permissions.
 
-class Extension;
 class ExtensionPermissionsInfo;
 
+namespace extensions {
+class Extension;
+}
+
 // When prompting the user to install or approve permissions, we display
 // messages describing the effects of the permissions rather than listing the
 // permissions themselves. Each ExtensionPermissionMessage represents one of the
@@ -290,7 +293,7 @@ class ExtensionPermissionSet
   // the api and host permissions (|apis| and |hosts|). The effective hosts
   // of the newly created permission set will be inferred from the |extension|
   // manifest, |apis| and |hosts|.
-  ExtensionPermissionSet(const Extension* extension,
+  ExtensionPermissionSet(const extensions::Extension* extension,
                          const ExtensionAPIPermissionSet& apis,
                          const URLPatternSet& explicit_hosts,
                          const ExtensionOAuth2Scopes& scopes);
@@ -411,7 +414,7 @@ class ExtensionPermissionSet
       bool exclude_file_scheme);
 
   // Initializes the set based on |extension|'s manifest data.
-  void InitImplicitExtensionPermissions(const Extension* extension);
+  void InitImplicitExtensionPermissions(const extensions::Extension* extension);
 
   // Initializes the effective host permission based on the data in this set.
   void InitEffectiveHosts();
diff --git a/chrome/common/extensions/extension_permission_set_unittest.cc b/chrome/common/extensions/extension_permission_set_unittest.cc
index dfd8ca8..dd85c5c 100644
--- a/chrome/common/extensions/extension_permission_set_unittest.cc
+++ b/chrome/common/extensions/extension_permission_set_unittest.cc
@@ -17,6 +17,8 @@
 #include "chrome/common/extensions/extension_permission_set.h"
 #include "testing/gtest/include/gtest/gtest.h"
 
+using extensions::Extension;
+
 namespace errors = extension_manifest_errors;
 namespace keys = extension_manifest_keys;
 namespace values = extension_manifest_values;
diff --git a/chrome/common/extensions/extension_process_policy.cc b/chrome/common/extensions/extension_process_policy.cc
index edadd0f..15a173a 100644
--- a/chrome/common/extensions/extension_process_policy.cc
+++ b/chrome/common/extensions/extension_process_policy.cc
@@ -8,10 +8,11 @@
 
 namespace extensions {
 
-const Extension* GetNonBookmarkAppExtension(
+const extensions::Extension* GetNonBookmarkAppExtension(
     const ExtensionSet& extensions, const ExtensionURLInfo& url) {
   // Exclude bookmark apps, which do not use the app process model.
-  const Extension* extension = extensions.GetExtensionOrAppByURL(url);
+  const extensions::Extension* extension =
+      extensions.GetExtensionOrAppByURL(url);
   if (extension && extension->from_bookmark())
     extension = NULL;
   return extension;
@@ -21,10 +22,12 @@ bool CrossesExtensionProcessBoundary(
     const ExtensionSet& extensions,
     const ExtensionURLInfo& old_url,
     const ExtensionURLInfo& new_url) {
-  const Extension* old_url_extension = GetNonBookmarkAppExtension(extensions,
-                                                                  old_url);
-  const Extension* new_url_extension = GetNonBookmarkAppExtension(extensions,
-                                                                  new_url);
+  const extensions::Extension* old_url_extension = GetNonBookmarkAppExtension(
+      extensions,
+      old_url);
+  const extensions::Extension* new_url_extension = GetNonBookmarkAppExtension(
+      extensions,
+      new_url);
 
   // TODO(creis): Temporary workaround for crbug.com/59285: Do not swap process
   // to navigate from a hosted app to a normal page or another hosted app
diff --git a/chrome/common/extensions/extension_process_policy.h b/chrome/common/extensions/extension_process_policy.h
index a2fc6f2..85f9eef 100644
--- a/chrome/common/extensions/extension_process_policy.h
+++ b/chrome/common/extensions/extension_process_policy.h
@@ -6,12 +6,13 @@
 #define CHROME_COMMON_EXTENSIONS_EXTENSION_PROCESS_POLICY_H_
 #pragma once
 
-class Extension;
 class ExtensionSet;
 class ExtensionURLInfo;
 
 namespace extensions {
 
+class Extension;
+
 // Returns the extension for the given URL.  Excludes extension objects for
 // bookmark apps, which do not use the app process model.
 const Extension* GetNonBookmarkAppExtension(const ExtensionSet& extensions,
diff --git a/chrome/common/extensions/extension_resource_unittest.cc b/chrome/common/extensions/extension_resource_unittest.cc
index 9b3e2d0..67c9ebd 100644
--- a/chrome/common/extensions/extension_resource_unittest.cc
+++ b/chrome/common/extensions/extension_resource_unittest.cc
@@ -116,7 +116,7 @@ TEST(ExtensionResourceTest, CreateWithAllResourcesOnDisk) {
   ASSERT_TRUE(file_util::WriteFile(root_resource, data.c_str(), data.length()));
 
   // Create l10n resources (for current locale and its parents).
-  FilePath l10n_path = temp.path().Append(Extension::kLocaleFolder);
+  FilePath l10n_path = temp.path().Append(extensions::Extension::kLocaleFolder);
   ASSERT_TRUE(file_util::CreateDirectory(l10n_path));
 
   std::vector<std::string> locales;
diff --git a/chrome/common/extensions/extension_set.cc b/chrome/common/extensions/extension_set.cc
index f5aee9f..1eb931c 100644
--- a/chrome/common/extensions/extension_set.cc
+++ b/chrome/common/extensions/extension_set.cc
@@ -5,9 +5,11 @@
 #include "chrome/common/extensions/extension_set.h"
 
 #include "base/logging.h"
+#include "chrome/common/extensions/extension.h"
 #include "chrome/common/url_constants.h"
 
 using WebKit::WebSecurityOrigin;
+using extensions::Extension;
 
 ExtensionURLInfo::ExtensionURLInfo(WebSecurityOrigin origin, const GURL& url)
   : origin_(origin),
diff --git a/chrome/common/extensions/extension_set.h b/chrome/common/extensions/extension_set.h
index 9d46373..428df7f 100644
--- a/chrome/common/extensions/extension_set.h
+++ b/chrome/common/extensions/extension_set.h
@@ -41,15 +41,16 @@ class ExtensionURLInfo {
 // The one true extension container. Extensions are identified by their id.
 // Only one extension can be in the set with a given ID.
 class ExtensionSet {
- public:
+public:
   typedef std::pair<FilePath, std::string> ExtensionPathAndDefaultLocale;
-  typedef std::map<std::string, scoped_refptr<const Extension> > ExtensionMap;
+  typedef std::map<std::string, scoped_refptr<const extensions::Extension> >
+      ExtensionMap;
 
   // Iteration over the values of the map (given that it's an ExtensionSet,
   // it should iterate like a set iterator).
   class const_iterator :
       public std::iterator<std::input_iterator_tag,
-                           scoped_refptr<const Extension> > {
+                           scoped_refptr<const extensions::Extension> > {
    public:
     const_iterator() {}
     explicit const_iterator(ExtensionMap::const_iterator it) :
@@ -58,7 +59,7 @@ class ExtensionSet {
       ++it_;
       return *this;
     }
-    const scoped_refptr<const Extension> operator*() {
+    const scoped_refptr<const extensions::Extension> operator*() {
       return it_->second;
     }
     bool operator!=(const const_iterator& other) { return it_ != other.it_; }
@@ -83,7 +84,7 @@ class ExtensionSet {
 
   // Adds the specified extension to the set. The set becomes an owner. Any
   // previous extension with the same ID is removed.
-  void Insert(const scoped_refptr<const Extension>& extension);
+  void Insert(const scoped_refptr<const extensions::Extension>& extension);
 
   // Copies different items from |extensions| to the current set and returns
   // whether anything changed.
@@ -104,14 +105,16 @@ class ExtensionSet {
   // NOTE: This can return NULL if called before UpdateExtensions receives
   // bulk extension data (e.g. if called from
   // EventBindings::HandleContextCreated)
-  const Extension* GetExtensionOrAppByURL(const ExtensionURLInfo& info) const;
+  const extensions::Extension* GetExtensionOrAppByURL(
+      const ExtensionURLInfo& info) const;
 
   // Returns the hosted app whose web extent contains the URL.
-  const Extension* GetHostedAppByURL(const ExtensionURLInfo& info) const;
+  const extensions::Extension* GetHostedAppByURL(
+      const ExtensionURLInfo& info) const;
 
   // Returns a hosted app that contains any URL that overlaps with the given
   // extent, if one exists.
-  const Extension* GetHostedAppByOverlappingWebExtent(
+  const extensions::Extension* GetHostedAppByOverlappingWebExtent(
       const URLPatternSet& extent) const;
 
   // Returns true if |new_url| is in the extent of the same extension as
@@ -119,7 +122,7 @@ class ExtensionSet {
   bool InSameExtent(const GURL& old_url, const GURL& new_url) const;
 
   // Look up an Extension object by id.
-  const Extension* GetByID(const std::string& id) const;
+  const extensions::Extension* GetByID(const std::string& id) const;
 
   // Returns true if |info| should get extension api bindings and be permitted
   // to make api calls. Note that this is independent of what extension
diff --git a/chrome/common/extensions/extension_set_unittest.cc b/chrome/common/extensions/extension_set_unittest.cc
index 37e5559..5d73d305 100644
--- a/chrome/common/extensions/extension_set_unittest.cc
+++ b/chrome/common/extensions/extension_set_unittest.cc
@@ -11,6 +11,8 @@
 #include "chrome/common/extensions/extension_set.h"
 #include "testing/gtest/include/gtest/gtest.h"
 
+using extensions::Extension;
+
 namespace {
 
 scoped_refptr<Extension> CreateTestExtension(const std::string& name,
diff --git a/chrome/common/extensions/extension_test_util.cc b/chrome/common/extensions/extension_test_util.cc
index 31f3af2..fc6562f 100644
--- a/chrome/common/extensions/extension_test_util.cc
+++ b/chrome/common/extensions/extension_test_util.cc
@@ -10,10 +10,10 @@ namespace extension_test_util {
 
 std::string MakeId(std::string seed) {
   std::string result;
-  bool success = Extension::GenerateId(seed, &result);
+  bool success = extensions::Extension::GenerateId(seed, &result);
   EXPECT_TRUE(success);
   EXPECT_FALSE(result.empty());
-  EXPECT_TRUE(Extension::IdIsValid(result));
+  EXPECT_TRUE(extensions::Extension::IdIsValid(result));
   return result;
 }
 
diff --git a/chrome/common/extensions/extension_unittest.cc b/chrome/common/extensions/extension_unittest.cc
index b72176c..9094670 100644
--- a/chrome/common/extensions/extension_unittest.cc
+++ b/chrome/common/extensions/extension_unittest.cc
@@ -27,6 +27,8 @@
 #include "third_party/skia/include/core/SkBitmap.h"
 #include "ui/gfx/codec/png_codec.h"
 
+using extensions::Extension;
+
 namespace keys = extension_manifest_keys;
 namespace values = extension_manifest_values;
 namespace errors = extension_manifest_errors;
diff --git a/chrome/common/extensions/extension_unpacker.cc b/chrome/common/extensions/extension_unpacker.cc
index 9e26808..5194b4b 100644
--- a/chrome/common/extensions/extension_unpacker.cc
+++ b/chrome/common/extensions/extension_unpacker.cc
@@ -86,7 +86,7 @@ bool PathContainsParentDirectory(const FilePath& path) {
 
 ExtensionUnpacker::ExtensionUnpacker(const FilePath& extension_path,
                                      const std::string& extension_id,
-                                     Extension::Location location,
+                                     extensions::Extension::Location location,
                                      int creation_flags)
     : extension_path_(extension_path),
       extension_id_(extension_id),
@@ -99,7 +99,7 @@ ExtensionUnpacker::~ExtensionUnpacker() {
 
 DictionaryValue* ExtensionUnpacker::ReadManifest() {
   FilePath manifest_path =
-      temp_install_dir_.Append(Extension::kManifestFilename);
+      temp_install_dir_.Append(extensions::Extension::kManifestFilename);
   if (!file_util::PathExists(manifest_path)) {
     SetError(errors::kInvalidManifest);
     return NULL;
@@ -124,7 +124,7 @@ DictionaryValue* ExtensionUnpacker::ReadManifest() {
 bool ExtensionUnpacker::ReadAllMessageCatalogs(
     const std::string& default_locale) {
   FilePath locales_path =
-    temp_install_dir_.Append(Extension::kLocaleFolder);
+    temp_install_dir_.Append(extensions::Extension::kLocaleFolder);
 
   // Not all folders under _locales have to be valid locales.
   file_util::FileEnumerator locales(locales_path,
@@ -140,7 +140,7 @@ bool ExtensionUnpacker::ReadAllMessageCatalogs(
       continue;
 
     FilePath messages_path =
-      locale_path.Append(Extension::kMessagesFilename);
+      locale_path.Append(extensions::Extension::kMessagesFilename);
 
     if (!ReadMessageCatalog(messages_path))
       return false;
@@ -178,7 +178,7 @@ bool ExtensionUnpacker::Run() {
     return false;  // Error was already reported.
 
   std::string error;
-  scoped_refptr<Extension> extension(Extension::Create(
+  scoped_refptr<extensions::Extension> extension(extensions::Extension::Create(
       temp_install_dir_,
       location_,
       *parsed_manifest_,
diff --git a/chrome/common/extensions/extension_unpacker.h b/chrome/common/extensions/extension_unpacker.h
index 5c6c14c..5fd7398 100644
--- a/chrome/common/extensions/extension_unpacker.h
+++ b/chrome/common/extensions/extension_unpacker.h
@@ -30,7 +30,7 @@ class ExtensionUnpacker {
 
   ExtensionUnpacker(const FilePath& extension_path,
                     const std::string& extension_id,
-                    Extension::Location location,
+                    extensions::Extension::Location location,
                     int creation_flags);
   ~ExtensionUnpacker();
 
@@ -93,7 +93,7 @@ class ExtensionUnpacker {
   std::string extension_id_;
 
   // The location to use for the created extension.
-  Extension::Location location_;
+  extensions::Extension::Location location_;
 
   // The creation flags to use with the created extension.
   int creation_flags_;
diff --git a/chrome/common/extensions/extension_unpacker_unittest.cc b/chrome/common/extensions/extension_unpacker_unittest.cc
index 4c43a7b..64d08f6 100644
--- a/chrome/common/extensions/extension_unpacker_unittest.cc
+++ b/chrome/common/extensions/extension_unpacker_unittest.cc
@@ -43,8 +43,10 @@ public:
         ", Crx path " << crx_path.value();
 
     unpacker_.reset(
-        new ExtensionUnpacker(
-            crx_path, std::string(), Extension::INTERNAL, Extension::NO_FLAGS));
+        new ExtensionUnpacker(crx_path,
+                              std::string(),
+                              extensions::Extension::INTERNAL,
+                              extensions::Extension::NO_FLAGS));
   }
 
  protected:
diff --git a/chrome/common/extensions/feature.cc b/chrome/common/extensions/feature.cc
index fabdc04..594a64e 100644
--- a/chrome/common/extensions/feature.cc
+++ b/chrome/common/extensions/feature.cc
@@ -12,6 +12,7 @@
 #include "chrome/common/chrome_switches.h"
 
 using chrome::VersionInfo;
+using extensions::Extension;
 
 namespace {
 
diff --git a/chrome/common/extensions/feature_unittest.cc b/chrome/common/extensions/feature_unittest.cc
index 1be05f3..a046124 100644
--- a/chrome/common/extensions/feature_unittest.cc
+++ b/chrome/common/extensions/feature_unittest.cc
@@ -7,6 +7,7 @@
 #include "testing/gtest/include/gtest/gtest.h"
 
 using chrome::VersionInfo;
+using extensions::Extension;
 using extensions::Feature;
 
 namespace {
diff --git a/chrome/common/extensions/manifest_tests/extension_manifest_test.cc b/chrome/common/extensions/manifest_tests/extension_manifest_test.cc
index 3237e2b..caef6c3 100644
--- a/chrome/common/extensions/manifest_tests/extension_manifest_test.cc
+++ b/chrome/common/extensions/manifest_tests/extension_manifest_test.cc
@@ -14,6 +14,8 @@
 #include "chrome/common/extensions/extension_l10n_util.h"
 #include "ui/base/l10n/l10n_util.h"
 
+using extensions::Extension;
+
 ExtensionManifestTest::ExtensionManifestTest() : enable_apps_(true) {}
 
 // static
diff --git a/chrome/common/extensions/manifest_tests/extension_manifest_test.h b/chrome/common/extensions/manifest_tests/extension_manifest_test.h
index f2222ad..b125dfa 100644
--- a/chrome/common/extensions/manifest_tests/extension_manifest_test.h
+++ b/chrome/common/extensions/manifest_tests/extension_manifest_test.h
@@ -54,36 +54,41 @@ class ExtensionManifestTest : public testing::Test {
     mutable scoped_ptr<DictionaryValue> manifest_holder_;
   };
 
-  scoped_refptr<Extension> LoadExtension(
+  scoped_refptr<extensions::Extension> LoadExtension(
       const Manifest& manifest,
       std::string* error,
-      Extension::Location location = Extension::INTERNAL,
-      int flags = Extension::NO_FLAGS);
+      extensions::Extension::Location location =
+          extensions::Extension::INTERNAL,
+      int flags = extensions::Extension::NO_FLAGS);
 
-  scoped_refptr<Extension> LoadAndExpectSuccess(
+  scoped_refptr<extensions::Extension> LoadAndExpectSuccess(
       const Manifest& manifest,
-      Extension::Location location = Extension::INTERNAL,
-      int flags = Extension::NO_FLAGS);
+      extensions::Extension::Location location =
+          extensions::Extension::INTERNAL,
+      int flags = extensions::Extension::NO_FLAGS);
 
-  scoped_refptr<Extension> LoadAndExpectSuccess(
+  scoped_refptr<extensions::Extension> LoadAndExpectSuccess(
       char const* manifest_name,
-      Extension::Location location = Extension::INTERNAL,
-      int flags = Extension::NO_FLAGS);
+      extensions::Extension::Location location =
+          extensions::Extension::INTERNAL,
+      int flags = extensions::Extension::NO_FLAGS);
 
-  void VerifyExpectedError(Extension* extension,
+  void VerifyExpectedError(extensions::Extension* extension,
                            const std::string& name,
                            const std::string& error,
                            const std::string& expected_error);
 
   void LoadAndExpectError(char const* manifest_name,
                           const std::string& expected_error,
-                          Extension::Location location = Extension::INTERNAL,
-                          int flags = Extension::NO_FLAGS);
+                          extensions::Extension::Location location =
+                              extensions::Extension::INTERNAL,
+                          int flags = extensions::Extension::NO_FLAGS);
 
   void LoadAndExpectError(const Manifest& manifest,
                           const std::string& expected_error,
-                          Extension::Location location = Extension::INTERNAL,
-                          int flags = Extension::NO_FLAGS);
+                          extensions::Extension::Location location =
+                              extensions::Extension::INTERNAL,
+                          int flags = extensions::Extension::NO_FLAGS);
 
   void AddPattern(URLPatternSet* extent, const std::string& pattern);
 
@@ -94,18 +99,19 @@ class ExtensionManifestTest : public testing::Test {
   struct Testcase {
     std::string manifest_filename_;
     std::string expected_error_; // only used for ExpectedError tests
-    Extension::Location location_;
+    extensions::Extension::Location location_;
     int flags_;
 
     Testcase(std::string manifest_filename, std::string expected_error,
-        Extension::Location location, int flags);
+        extensions::Extension::Location location, int flags);
 
     Testcase(std::string manifest_filename, std::string expected_error);
 
     explicit Testcase(std::string manifest_filename);
 
-    Testcase(std::string manifest_filename, Extension::Location location,
-        int flags);
+    Testcase(std::string manifest_filename,
+             extensions::Extension::Location location,
+             int flags);
   };
 
   void RunTestcases(const Testcase* testcases, size_t num_testcases,
diff --git a/chrome/common/extensions/manifest_tests/extension_manifests_chromepermission_unittest.cc b/chrome/common/extensions/manifest_tests/extension_manifests_chromepermission_unittest.cc
index e9e329e..691c477 100644
--- a/chrome/common/extensions/manifest_tests/extension_manifests_chromepermission_unittest.cc
+++ b/chrome/common/extensions/manifest_tests/extension_manifests_chromepermission_unittest.cc
@@ -21,7 +21,7 @@ TEST_F(ExtensionManifestTest, ChromeResourcesPermissionValidOnlyForComponents) {
   std::string error;
   LoadExtension(Manifest("permission_chrome_resources_url.json"),
                 &error,
-                Extension::COMPONENT,
-                Extension::STRICT_ERROR_CHECKS);
+                extensions::Extension::COMPONENT,
+                extensions::Extension::STRICT_ERROR_CHECKS);
   EXPECT_EQ("", error);
 }
diff --git a/chrome/common/extensions/manifest_tests/extension_manifests_default_unittest.cc b/chrome/common/extensions/manifest_tests/extension_manifests_default_unittest.cc
index 5152bbf..959a161 100644
--- a/chrome/common/extensions/manifest_tests/extension_manifests_default_unittest.cc
+++ b/chrome/common/extensions/manifest_tests/extension_manifests_default_unittest.cc
@@ -11,7 +11,7 @@
 namespace errors = extension_manifest_errors;
 
 TEST_F(ExtensionManifestTest, DefaultPathForExtent) {
-  scoped_refptr<Extension> extension(
+  scoped_refptr<extensions::Extension> extension(
       LoadAndExpectSuccess("default_path_for_extent.json"));
 
   ASSERT_EQ(1u, extension->web_extent().patterns().size());
@@ -24,7 +24,7 @@ TEST_F(ExtensionManifestTest, DefaultLocale) {
   LoadAndExpectError("default_locale_invalid.json",
                      errors::kInvalidDefaultLocale);
 
-  scoped_refptr<Extension> extension(
+  scoped_refptr<extensions::Extension> extension(
       LoadAndExpectSuccess("default_locale_valid.json"));
   EXPECT_EQ("de-AT", extension->default_locale());
 }
diff --git a/chrome/common/extensions/manifest_tests/extension_manifests_devtools_unittest.cc b/chrome/common/extensions/manifest_tests/extension_manifests_devtools_unittest.cc
index 5e027b5..4ee81e7 100644
--- a/chrome/common/extensions/manifest_tests/extension_manifests_devtools_unittest.cc
+++ b/chrome/common/extensions/manifest_tests/extension_manifests_devtools_unittest.cc
@@ -14,7 +14,7 @@ TEST_F(ExtensionManifestTest, DevToolsExtensions) {
   LoadAndExpectError("devtools_extension_url_invalid_type.json",
                      errors::kInvalidDevToolsPage);
 
-  scoped_refptr<Extension> extension;
+  scoped_refptr<extensions::Extension> extension;
   extension = LoadAndExpectSuccess("devtools_extension.json");
   EXPECT_EQ(extension->url().spec() + "devtools.html",
             extension->devtools_url().spec());
diff --git a/chrome/common/extensions/manifest_tests/extension_manifests_experimental_unittest.cc b/chrome/common/extensions/manifest_tests/extension_manifests_experimental_unittest.cc
index 57b7f7d..4fe31c4 100644
--- a/chrome/common/extensions/manifest_tests/extension_manifests_experimental_unittest.cc
+++ b/chrome/common/extensions/manifest_tests/extension_manifests_experimental_unittest.cc
@@ -14,9 +14,9 @@ namespace errors = extension_manifest_errors;
 
 TEST_F(ExtensionManifestTest, ExperimentalPermission) {
   LoadAndExpectError("experimental.json", errors::kExperimentalFlagRequired);
-  LoadAndExpectSuccess("experimental.json", Extension::COMPONENT);
-  LoadAndExpectSuccess("experimental.json", Extension::INTERNAL,
-                       Extension::FROM_WEBSTORE);
+  LoadAndExpectSuccess("experimental.json", extensions::Extension::COMPONENT);
+  LoadAndExpectSuccess("experimental.json", extensions::Extension::INTERNAL,
+                       extensions::Extension::FROM_WEBSTORE);
   CommandLine::ForCurrentProcess()->AppendSwitch(
       switches::kEnableExperimentalExtensionApis);
   LoadAndExpectSuccess("experimental.json");
diff --git a/chrome/common/extensions/manifest_tests/extension_manifests_filebrowser_unittest.cc b/chrome/common/extensions/manifest_tests/extension_manifests_filebrowser_unittest.cc
index eaa227c..3668d35 100644
--- a/chrome/common/extensions/manifest_tests/extension_manifests_filebrowser_unittest.cc
+++ b/chrome/common/extensions/manifest_tests/extension_manifests_filebrowser_unittest.cc
@@ -11,6 +11,8 @@
 #include "chrome/common/extensions/file_browser_handler.h"
 #include "testing/gtest/include/gtest/gtest.h"
 
+using extensions::Extension;
+
 namespace errors = extension_manifest_errors;
 
 TEST_F(ExtensionManifestTest, FileBrowserHandlers) {
diff --git a/chrome/common/extensions/manifest_tests/extension_manifests_homepage_unittest.cc b/chrome/common/extensions/manifest_tests/extension_manifests_homepage_unittest.cc
index 66c3c42..59836af 100644
--- a/chrome/common/extensions/manifest_tests/extension_manifests_homepage_unittest.cc
+++ b/chrome/common/extensions/manifest_tests/extension_manifests_homepage_unittest.cc
@@ -12,7 +12,7 @@
 namespace errors = extension_manifest_errors;
 
 TEST_F(ExtensionManifestTest, ParseHomepageURLs) {
-  scoped_refptr<Extension> extension(
+  scoped_refptr<extensions::Extension> extension(
       LoadAndExpectSuccess("homepage_valid.json"));
 
   Testcase testcases[] = {
@@ -28,7 +28,7 @@ TEST_F(ExtensionManifestTest, ParseHomepageURLs) {
 }
 
 TEST_F(ExtensionManifestTest, GetHomepageURL) {
-  scoped_refptr<Extension> extension(
+  scoped_refptr<extensions::Extension> extension(
       LoadAndExpectSuccess("homepage_valid.json"));
   EXPECT_EQ(GURL("http://foo.com#bar"), extension->GetHomepageURL());
 
diff --git a/chrome/common/extensions/manifest_tests/extension_manifests_icon_unittest.cc b/chrome/common/extensions/manifest_tests/extension_manifests_icon_unittest.cc
index 4e9d570..23c05fd 100644
--- a/chrome/common/extensions/manifest_tests/extension_manifests_icon_unittest.cc
+++ b/chrome/common/extensions/manifest_tests/extension_manifests_icon_unittest.cc
@@ -8,7 +8,7 @@
 #include "testing/gtest/include/gtest/gtest.h"
 
 TEST_F(ExtensionManifestTest, NormalizeIconPaths) {
-  scoped_refptr<Extension> extension(
+  scoped_refptr<extensions::Extension> extension(
       LoadAndExpectSuccess("normalize_icon_paths.json"));
   EXPECT_EQ("16.png", extension->icons().Get(
       ExtensionIconSet::EXTENSION_ICON_BITTY, ExtensionIconSet::MATCH_EXACTLY));
@@ -18,7 +18,7 @@ TEST_F(ExtensionManifestTest, NormalizeIconPaths) {
 }
 
 TEST_F(ExtensionManifestTest, InvalidIconSizes) {
-  scoped_refptr<Extension> extension(
+  scoped_refptr<extensions::Extension> extension(
       LoadAndExpectSuccess("init_ignored_icon_size.json"));
   EXPECT_EQ("", extension->icons().Get(
       static_cast<ExtensionIconSet::Icons>(300),
@@ -26,7 +26,7 @@ TEST_F(ExtensionManifestTest, InvalidIconSizes) {
 }
 
 TEST_F(ExtensionManifestTest, ValidIconSizes) {
-  scoped_refptr<Extension> extension(
+  scoped_refptr<extensions::Extension> extension(
       LoadAndExpectSuccess("init_valid_icon_size.json"));
   EXPECT_EQ("16.png", extension->icons().Get(
       ExtensionIconSet::EXTENSION_ICON_BITTY, ExtensionIconSet::MATCH_EXACTLY));
diff --git a/chrome/common/extensions/manifest_tests/extension_manifests_initvalue_unittest.cc b/chrome/common/extensions/manifest_tests/extension_manifests_initvalue_unittest.cc
index 0840c87..588017b 100644
--- a/chrome/common/extensions/manifest_tests/extension_manifests_initvalue_unittest.cc
+++ b/chrome/common/extensions/manifest_tests/extension_manifests_initvalue_unittest.cc
@@ -74,14 +74,14 @@ TEST_F(ExtensionManifestTest, InitFromValueInvalid) {
 }
 
 TEST_F(ExtensionManifestTest, InitFromValueValid) {
-  scoped_refptr<Extension> extension(LoadAndExpectSuccess(
+  scoped_refptr<extensions::Extension> extension(LoadAndExpectSuccess(
       "init_valid_minimal.json"));
 
   FilePath path;
   PathService::Get(chrome::DIR_TEST_DATA, &path);
   path = path.AppendASCII("extensions");
 
-  EXPECT_TRUE(Extension::IdIsValid(extension->id()));
+  EXPECT_TRUE(extensions::Extension::IdIsValid(extension->id()));
   EXPECT_EQ("1.0.0.0", extension->VersionString());
   EXPECT_EQ("my extension", extension->name());
   EXPECT_EQ(extension->id(), extension->url().host());
@@ -134,7 +134,7 @@ TEST_F(ExtensionManifestTest, InitFromValueValidNameInRTL) {
 #endif
 
   // No strong RTL characters in name.
-  scoped_refptr<Extension> extension(LoadAndExpectSuccess(
+  scoped_refptr<extensions::Extension> extension(LoadAndExpectSuccess(
       "init_valid_name_no_rtl.json"));
 
   string16 localized_name(ASCIIToUTF16("Dictionary (by Google)"));
diff --git a/chrome/common/extensions/manifest_tests/extension_manifests_isolatedapp_unittest.cc b/chrome/common/extensions/manifest_tests/extension_manifests_isolatedapp_unittest.cc
index a93dbaf..6181ad0 100644
--- a/chrome/common/extensions/manifest_tests/extension_manifests_isolatedapp_unittest.cc
+++ b/chrome/common/extensions/manifest_tests/extension_manifests_isolatedapp_unittest.cc
@@ -19,7 +19,7 @@ TEST_F(ExtensionManifestTest, IsolatedApps) {
 
   CommandLine::ForCurrentProcess()->AppendSwitch(
       switches::kEnableExperimentalExtensionApis);
-  scoped_refptr<Extension> extension2(
+  scoped_refptr<extensions::Extension> extension2(
       LoadAndExpectSuccess("isolated_app_valid.json"));
   EXPECT_TRUE(extension2->is_storage_isolated());
 }
diff --git a/chrome/common/extensions/manifest_tests/extension_manifests_launch_unittest.cc b/chrome/common/extensions/manifest_tests/extension_manifests_launch_unittest.cc
index 84cdf8d..35df234 100644
--- a/chrome/common/extensions/manifest_tests/extension_manifests_launch_unittest.cc
+++ b/chrome/common/extensions/manifest_tests/extension_manifests_launch_unittest.cc
@@ -14,7 +14,7 @@
 namespace errors = extension_manifest_errors;
 
 TEST_F(ExtensionManifestTest, AppLaunchContainer) {
-  scoped_refptr<Extension> extension;
+  scoped_refptr<extensions::Extension> extension;
 
   extension = LoadAndExpectSuccess("launch_tab.json");
   EXPECT_EQ(extension_misc::LAUNCH_TAB, extension->launch_container());
@@ -98,7 +98,7 @@ TEST_F(ExtensionManifestTest, AppLaunchURL) {
   RunTestcases(testcases, arraysize(testcases),
       EXPECT_TYPE_ERROR);
 
-  scoped_refptr<Extension> extension;
+  scoped_refptr<extensions::Extension> extension;
   extension = LoadAndExpectSuccess("launch_local_path.json");
   EXPECT_EQ(extension->url().spec() + "launch.html",
             extension->GetFullLaunchURL().spec());
diff --git a/chrome/common/extensions/manifest_tests/extension_manifests_offline_unittest.cc b/chrome/common/extensions/manifest_tests/extension_manifests_offline_unittest.cc
index 9f7f031..7ec1c37 100644
--- a/chrome/common/extensions/manifest_tests/extension_manifests_offline_unittest.cc
+++ b/chrome/common/extensions/manifest_tests/extension_manifests_offline_unittest.cc
@@ -8,6 +8,8 @@
 #include "chrome/common/extensions/extension_manifest_constants.h"
 #include "testing/gtest/include/gtest/gtest.h"
 
+using extensions::Extension;
+
 namespace errors = extension_manifest_errors;
 
 TEST_F(ExtensionManifestTest, OfflineEnabled) {
diff --git a/chrome/common/extensions/manifest_tests/extension_manifests_old_unittest.cc b/chrome/common/extensions/manifest_tests/extension_manifests_old_unittest.cc
index 4664f89..bd590c5 100644
--- a/chrome/common/extensions/manifest_tests/extension_manifests_old_unittest.cc
+++ b/chrome/common/extensions/manifest_tests/extension_manifests_old_unittest.cc
@@ -10,10 +10,10 @@
 // Tests that the old permission name "unlimited_storage" still works for
 // backwards compatibility (we renamed it to "unlimitedStorage").
 TEST_F(ExtensionManifestTest, OldUnlimitedStoragePermission) {
-  scoped_refptr<Extension> extension = LoadAndExpectSuccess(
+  scoped_refptr<extensions::Extension> extension = LoadAndExpectSuccess(
       "old_unlimited_storage.json",
-      Extension::INTERNAL,
-      Extension::STRICT_ERROR_CHECKS);
+      extensions::Extension::INTERNAL,
+      extensions::Extension::STRICT_ERROR_CHECKS);
   EXPECT_TRUE(extension->HasAPIPermission(
       ExtensionAPIPermission::kUnlimitedStorage));
 }
diff --git a/chrome/common/extensions/manifest_tests/extension_manifests_options_unittest.cc b/chrome/common/extensions/manifest_tests/extension_manifests_options_unittest.cc
index 5853fda..2eef91d 100644
--- a/chrome/common/extensions/manifest_tests/extension_manifests_options_unittest.cc
+++ b/chrome/common/extensions/manifest_tests/extension_manifests_options_unittest.cc
@@ -10,7 +10,7 @@
 namespace errors = extension_manifest_errors;
 
 TEST_F(ExtensionManifestTest, OptionsPageInApps) {
-  scoped_refptr<Extension> extension;
+  scoped_refptr<extensions::Extension> extension;
 
   // Allow options page with absolute URL in hosted apps.
   extension = LoadAndExpectSuccess("hosted_app_absolute_options.json");
diff --git a/chrome/common/extensions/manifest_tests/extension_manifests_override_unittest.cc b/chrome/common/extensions/manifest_tests/extension_manifests_override_unittest.cc
index 0fb2e52..b7d4c0e 100644
--- a/chrome/common/extensions/manifest_tests/extension_manifests_override_unittest.cc
+++ b/chrome/common/extensions/manifest_tests/extension_manifests_override_unittest.cc
@@ -17,7 +17,7 @@ TEST_F(ExtensionManifestTest, Override) {
   RunTestcases(testcases, arraysize(testcases),
                EXPECT_TYPE_ERROR);
 
-  scoped_refptr<Extension> extension;
+  scoped_refptr<extensions::Extension> extension;
 
   extension = LoadAndExpectSuccess("override_new_tab.json");
   EXPECT_EQ(extension->url().spec() + "newtab.html",
diff --git a/chrome/common/extensions/manifest_tests/extension_manifests_pageaction_unittest.cc b/chrome/common/extensions/manifest_tests/extension_manifests_pageaction_unittest.cc
index 4ecd8f9..fccc493 100644
--- a/chrome/common/extensions/manifest_tests/extension_manifests_pageaction_unittest.cc
+++ b/chrome/common/extensions/manifest_tests/extension_manifests_pageaction_unittest.cc
@@ -11,7 +11,7 @@
 namespace errors = extension_manifest_errors;
 
 TEST_F(ExtensionManifestTest, PageActionManifestVersion2) {
-  scoped_refptr<Extension> extension(
+  scoped_refptr<extensions::Extension> extension(
       LoadAndExpectSuccess("page_action_manifest_version_2.json"));
   ASSERT_TRUE(extension.get());
   ASSERT_TRUE(extension->page_action());
diff --git a/chrome/common/extensions/manifest_tests/extension_manifests_platformapp_unittest.cc b/chrome/common/extensions/manifest_tests/extension_manifests_platformapp_unittest.cc
index 8b39de3..ab7a852 100644
--- a/chrome/common/extensions/manifest_tests/extension_manifests_platformapp_unittest.cc
+++ b/chrome/common/extensions/manifest_tests/extension_manifests_platformapp_unittest.cc
@@ -20,7 +20,7 @@ TEST_F(ExtensionManifestTest, PlatformApps) {
 
   CommandLine::ForCurrentProcess()->AppendSwitch(switches::kEnablePlatformApps);
 
-  scoped_refptr<Extension> extension =
+  scoped_refptr<extensions::Extension> extension =
       LoadAndExpectSuccess("init_valid_platform_app.json");
   EXPECT_TRUE(extension->is_storage_isolated());
 
diff --git a/chrome/common/extensions/manifest_tests/extension_manifests_storage_unittest.cc b/chrome/common/extensions/manifest_tests/extension_manifests_storage_unittest.cc
index 8acb36c..e020bf0 100644
--- a/chrome/common/extensions/manifest_tests/extension_manifests_storage_unittest.cc
+++ b/chrome/common/extensions/manifest_tests/extension_manifests_storage_unittest.cc
@@ -25,7 +25,8 @@ TEST_F(ExtensionManifestTest, StorageAPIManifestVersionAvailability) {
   // Extension with no manifest version cannot use storage API.
   {
     Manifest manifest(&base_manifest, "test");
-    scoped_refptr<Extension> extension = LoadAndExpectSuccess(manifest);
+    scoped_refptr<extensions::Extension> extension =
+        LoadAndExpectSuccess(manifest);
     if (extension.get()) {
       std::vector<std::string> warnings;
       warnings.push_back(kManifestVersionError);
@@ -40,7 +41,8 @@ TEST_F(ExtensionManifestTest, StorageAPIManifestVersionAvailability) {
     manifest_with_version.MergeDictionary(&base_manifest);
 
     Manifest manifest(&manifest_with_version, "test");
-    scoped_refptr<Extension> extension = LoadAndExpectSuccess(manifest);
+    scoped_refptr<extensions::Extension> extension =
+        LoadAndExpectSuccess(manifest);
     if (extension.get()) {
       std::vector<std::string> warnings;
       warnings.push_back(kManifestVersionError);
@@ -55,7 +57,8 @@ TEST_F(ExtensionManifestTest, StorageAPIManifestVersionAvailability) {
     manifest_with_version.MergeDictionary(&base_manifest);
 
     Manifest manifest(&manifest_with_version, "test");
-    scoped_refptr<Extension> extension = LoadAndExpectSuccess(manifest);
+    scoped_refptr<extensions::Extension> extension =
+        LoadAndExpectSuccess(manifest);
     if (extension.get()) {
       std::vector<std::string> empty;
       EXPECT_EQ(empty, extension->install_warnings());
diff --git a/chrome/common/extensions/manifest_tests/extension_manifests_tts_unittest.cc b/chrome/common/extensions/manifest_tests/extension_manifests_tts_unittest.cc
index fd71dd1..954a172 100644
--- a/chrome/common/extensions/manifest_tests/extension_manifests_tts_unittest.cc
+++ b/chrome/common/extensions/manifest_tests/extension_manifests_tts_unittest.cc
@@ -33,7 +33,7 @@ TEST_F(ExtensionManifestTest, TtsEngine) {
   RunTestcases(testcases, arraysize(testcases),
                EXPECT_TYPE_ERROR);
 
-  scoped_refptr<Extension> extension(
+  scoped_refptr<extensions::Extension> extension(
       LoadAndExpectSuccess("tts_engine_valid.json"));
 
   ASSERT_EQ(1u, extension->tts_voices().size());
diff --git a/chrome/common/extensions/manifest_tests/extension_manifests_update_unittest.cc b/chrome/common/extensions/manifest_tests/extension_manifests_update_unittest.cc
index 5f3f9d0..6d44698 100644
--- a/chrome/common/extensions/manifest_tests/extension_manifests_update_unittest.cc
+++ b/chrome/common/extensions/manifest_tests/extension_manifests_update_unittest.cc
@@ -7,6 +7,8 @@
 #include "chrome/common/extensions/extension_manifest_constants.h"
 #include "testing/gtest/include/gtest/gtest.h"
 
+using extensions::Extension;
+
 namespace errors = extension_manifest_errors;
 
 TEST_F(ExtensionManifestTest, UpdateUrls) {
diff --git a/chrome/common/extensions/manifest_tests/extension_manifests_validapp_unittest.cc b/chrome/common/extensions/manifest_tests/extension_manifests_validapp_unittest.cc
index 9eb971e..f8bd6d5 100644
--- a/chrome/common/extensions/manifest_tests/extension_manifests_validapp_unittest.cc
+++ b/chrome/common/extensions/manifest_tests/extension_manifests_validapp_unittest.cc
@@ -9,7 +9,8 @@
 #include "testing/gtest/include/gtest/gtest.h"
 
 TEST_F(ExtensionManifestTest, ValidApp) {
-  scoped_refptr<Extension> extension(LoadAndExpectSuccess("valid_app.json"));
+  scoped_refptr<extensions::Extension> extension(
+      LoadAndExpectSuccess("valid_app.json"));
   URLPatternSet expected_patterns;
   AddPattern(&expected_patterns, "http://www.google.com/mail/*");
   AddPattern(&expected_patterns, "http://www.google.com/foobar/*");
diff --git a/chrome/common/extensions/manifest_tests/extension_manifests_web_unittest.cc b/chrome/common/extensions/manifest_tests/extension_manifests_web_unittest.cc
index 59ca69c..879c537 100644
--- a/chrome/common/extensions/manifest_tests/extension_manifests_web_unittest.cc
+++ b/chrome/common/extensions/manifest_tests/extension_manifests_web_unittest.cc
@@ -11,6 +11,8 @@
 #include "testing/gtest/include/gtest/gtest.h"
 #include "webkit/glue/web_intent_service_data.h"
 
+using extensions::Extension;
+
 namespace errors = extension_manifest_errors;
 
 TEST_F(ExtensionManifestTest, WebAccessibleResources) {
diff --git a/chrome/common/extensions/simple_feature_provider_unittest.cc b/chrome/common/extensions/simple_feature_provider_unittest.cc
index 3d9dd72..fd0fd34 100644
--- a/chrome/common/extensions/simple_feature_provider_unittest.cc
+++ b/chrome/common/extensions/simple_feature_provider_unittest.cc
@@ -6,6 +6,7 @@
 
 #include "testing/gtest/include/gtest/gtest.h"
 
+using extensions::Extension;
 using extensions::Feature;
 using extensions::SimpleFeatureProvider;
 
diff --git a/chrome/renderer/chrome_content_renderer_client.cc b/chrome/renderer/chrome_content_renderer_client.cc
index ddd22ac..aef61cd 100644
--- a/chrome/renderer/chrome_content_renderer_client.cc
+++ b/chrome/renderer/chrome_content_renderer_client.cc
@@ -88,12 +88,19 @@
 #include "webkit/plugins/ppapi/plugin_module.h"
 #include "webkit/plugins/ppapi/ppapi_interface_factory.h"
 
+using autofill::AutofillAgent;
+using autofill::PasswordAutofillManager;
+using autofill::PasswordGenerationManager;
+using content::RenderThread;
+using extensions::Extension;
 using WebKit::WebCache;
 using WebKit::WebConsoleMessage;
 using WebKit::WebDataSource;
 using WebKit::WebDocument;
 using WebKit::WebFrame;
 using WebKit::WebPlugin;
+using webkit::WebPluginInfo;
+using webkit::WebPluginMimeType;
 using WebKit::WebPluginParams;
 using WebKit::WebSecurityOrigin;
 using WebKit::WebSecurityPolicy;
@@ -103,12 +110,6 @@ using WebKit::WebURLError;
 using WebKit::WebURLRequest;
 using WebKit::WebURLResponse;
 using WebKit::WebVector;
-using autofill::AutofillAgent;
-using autofill::PasswordAutofillManager;
-using autofill::PasswordGenerationManager;
-using content::RenderThread;
-using webkit::WebPluginInfo;
-using webkit::WebPluginMimeType;
 
 namespace {
 
diff --git a/chrome/renderer/chrome_content_renderer_client.h b/chrome/renderer/chrome_content_renderer_client.h
index c587e70..17fea34 100644
--- a/chrome/renderer/chrome_content_renderer_client.h
+++ b/chrome/renderer/chrome_content_renderer_client.h
@@ -15,7 +15,6 @@
 #include "content/public/renderer/content_renderer_client.h"
 
 class ChromeRenderProcessObserver;
-class Extension;
 class ExtensionDispatcher;
 class ExtensionSet;
 class RendererHistogramSnapshots;
diff --git a/chrome/renderer/extensions/app_bindings.cc b/chrome/renderer/extensions/app_bindings.cc
index f69d2ef..550421e 100644
--- a/chrome/renderer/extensions/app_bindings.cc
+++ b/chrome/renderer/extensions/app_bindings.cc
@@ -25,6 +25,7 @@
 
 using WebKit::WebFrame;
 using content::V8ValueConverter;
+using extensions::Extension;
 
 namespace {
 
@@ -77,7 +78,7 @@ AppBindings::AppBindings(ExtensionDispatcher* dispatcher,
 
 v8::Handle<v8::Value> AppBindings::GetIsInstalled(
     const v8::Arguments& args) {
-  const Extension* extension = context_->extension();
+  const extensions::Extension* extension = context_->extension();
 
   // TODO(aa): Why only hosted app?
   bool result = extension && extension->is_hosted_app() &&
@@ -134,7 +135,7 @@ v8::Handle<v8::Value> AppBindings::GetDetailsForFrame(
 
 v8::Handle<v8::Value> AppBindings::GetDetailsForFrameImpl(
     WebFrame* frame) {
-  const ::Extension* extension =
+  const extensions::Extension* extension =
       extension_dispatcher_->extensions()->GetExtensionOrAppByURL(
           ExtensionURLInfo(frame->document().securityOrigin(),
                            frame->document().url()));
diff --git a/chrome/renderer/extensions/chrome_v8_context.cc b/chrome/renderer/extensions/chrome_v8_context.cc
index 599b235..6d037fa 100644
--- a/chrome/renderer/extensions/chrome_v8_context.cc
+++ b/chrome/renderer/extensions/chrome_v8_context.cc
@@ -9,6 +9,7 @@
 #include "base/string_split.h"
 #include "base/values.h"
 #include "chrome/common/extensions/api/extension_api.h"
+#include "chrome/common/extensions/extension.h"
 #include "chrome/common/extensions/extension_set.h"
 #include "chrome/renderer/extensions/chrome_v8_extension.h"
 #include "chrome/renderer/extensions/user_script_slave.h"
@@ -44,7 +45,7 @@ std::string GetContextTypeDescription(Feature::Context context_type) {
 
 ChromeV8Context::ChromeV8Context(v8::Handle<v8::Context> v8_context,
                                  WebKit::WebFrame* web_frame,
-                                 const Extension* extension,
+                                 const extensions::Extension* extension,
                                  Feature::Context context_type)
     : v8_context_(v8::Persistent<v8::Context>::New(v8_context)),
       web_frame_(web_frame),
diff --git a/chrome/renderer/extensions/chrome_v8_context.h b/chrome/renderer/extensions/chrome_v8_context.h
index 4795688..8aec582 100644
--- a/chrome/renderer/extensions/chrome_v8_context.h
+++ b/chrome/renderer/extensions/chrome_v8_context.h
@@ -21,6 +21,10 @@ namespace content {
 class RenderView;
 }
 
+namespace extensions {
+class Extension;
+}
+
 // Chrome's wrapper for a v8 context.
 //
 // TODO(aa): Consider converting this back to a set of bindings_utils. It would
@@ -30,7 +34,7 @@ class ChromeV8Context {
  public:
   ChromeV8Context(v8::Handle<v8::Context> context,
                   WebKit::WebFrame* frame,
-                  const Extension* extension,
+                  const extensions::Extension* extension,
                   extensions::Feature::Context context_type);
   ~ChromeV8Context();
 
@@ -38,7 +42,7 @@ class ChromeV8Context {
     return v8_context_;
   }
 
-  const Extension* extension() const {
+  const extensions::Extension* extension() const {
     return extension_.get();
   }
 
@@ -114,7 +118,7 @@ class ChromeV8Context {
 
   // The extension associated with this context, or NULL if there is none. This
   // might be a hosted app in the case that this context is hosting a web URL.
-  scoped_refptr<const Extension> extension_;
+  scoped_refptr<const extensions::Extension> extension_;
 
   // The type of context.
   extensions::Feature::Context context_type_;
diff --git a/chrome/renderer/extensions/chrome_v8_context_set.cc b/chrome/renderer/extensions/chrome_v8_context_set.cc
index bbb8a41..dfe3d85 100644
--- a/chrome/renderer/extensions/chrome_v8_context_set.cc
+++ b/chrome/renderer/extensions/chrome_v8_context_set.cc
@@ -8,6 +8,7 @@
 #include "base/message_loop.h"
 #include "base/tracked_objects.h"
 #include "base/values.h"
+#include "chrome/common/extensions/extension.h"
 #include "chrome/common/url_constants.h"
 #include "chrome/renderer/extensions/chrome_v8_context.h"
 #include "content/public/renderer/render_thread.h"
@@ -118,7 +119,7 @@ void ChromeV8ContextSet::DispatchChromeHiddenMethod(
       continue;
 
     if (!extension_id.empty()) {
-      const Extension* extension = (*it)->extension();
+      const extensions::Extension* extension = (*it)->extension();
       if (!extension || (extension_id != extension->id()))
         continue;
     }
diff --git a/chrome/renderer/extensions/chrome_v8_context_set_unittest.cc b/chrome/renderer/extensions/chrome_v8_context_set_unittest.cc
index 92443aa..1a53a27 100644
--- a/chrome/renderer/extensions/chrome_v8_context_set_unittest.cc
+++ b/chrome/renderer/extensions/chrome_v8_context_set_unittest.cc
@@ -22,7 +22,7 @@ TEST(ChromeV8ContextSet, Lifecycle) {
   // Dirty hack, but we don't actually need the frame, and this is easier than
   // creating a whole webview.
   WebKit::WebFrame* frame = reinterpret_cast<WebKit::WebFrame*>(1);
-  const Extension* extension = NULL;
+  const extensions::Extension* extension = NULL;
   ChromeV8Context* context = new ChromeV8Context(
       v8_context,
       frame,
diff --git a/chrome/renderer/extensions/chrome_v8_extension.cc b/chrome/renderer/extensions/chrome_v8_extension.cc
index 486d68b..d4bcbf0 100644
--- a/chrome/renderer/extensions/chrome_v8_extension.cc
+++ b/chrome/renderer/extensions/chrome_v8_extension.cc
@@ -62,7 +62,8 @@ const ChromeV8Extension::InstanceSet& ChromeV8Extension::GetAll() {
   return g_instances.Get();
 }
 
-const Extension* ChromeV8Extension::GetExtensionForCurrentRenderView() const {
+const extensions::Extension*
+    ChromeV8Extension::GetExtensionForCurrentRenderView() const {
   content::RenderView* renderview = GetCurrentRenderView();
   if (!renderview)
     return NULL;  // this can happen as a tab is closing.
diff --git a/chrome/renderer/extensions/chrome_v8_extension.h b/chrome/renderer/extensions/chrome_v8_extension.h
index 84fda03..4be6587 100644
--- a/chrome/renderer/extensions/chrome_v8_extension.h
+++ b/chrome/renderer/extensions/chrome_v8_extension.h
@@ -18,13 +18,16 @@
 #include <string>
 
 class ChromeV8Context;
-class Extension;
 class ExtensionDispatcher;
 
 namespace content {
 class RenderView;
 }
 
+namespace extensions {
+class Extension;
+}
+
 // This is a base class for chrome extension bindings.  Common features that
 // are shared by different modules go here.
 // TODO(koz): Rename this to ExtensionNativeModule.
@@ -52,7 +55,7 @@ class ChromeV8Extension : public NativeHandler {
   // Note: do not call this function before or during the chromeHidden.onLoad
   // event dispatch. The URL might not have been committed yet and might not
   // be an extension URL.
-  const ::Extension* GetExtensionForCurrentRenderView() const;
+  const extensions::Extension* GetExtensionForCurrentRenderView() const;
 
   // Returns the chromeHidden object for the current context.
   static v8::Handle<v8::Value> GetChromeHidden(const v8::Arguments& args);
diff --git a/chrome/renderer/extensions/event_bindings.cc b/chrome/renderer/extensions/event_bindings.cc
index 478c7f2..ac5b0aa 100644
--- a/chrome/renderer/extensions/event_bindings.cc
+++ b/chrome/renderer/extensions/event_bindings.cc
@@ -35,6 +35,7 @@ using WebKit::WebFrame;
 using WebKit::WebSecurityOrigin;
 using WebKit::WebURL;
 using content::RenderThread;
+using extensions::Extension;
 
 namespace {
 
diff --git a/chrome/renderer/extensions/extension_custom_bindings.cc b/chrome/renderer/extensions/extension_custom_bindings.cc
index f60a497..a301342 100644
--- a/chrome/renderer/extensions/extension_custom_bindings.cc
+++ b/chrome/renderer/extensions/extension_custom_bindings.cc
@@ -8,6 +8,7 @@
 
 #include "base/string_util.h"
 #include "chrome/common/chrome_view_type.h"
+#include "chrome/common/extensions/extension.h"
 #include "chrome/common/extensions/extension_action.h"
 #include "chrome/common/extensions/extension_messages.h"
 #include "chrome/common/url_constants.h"
@@ -73,7 +74,7 @@ v8::Handle<v8::Value> ExtensionCustomBindings::GetExtensionViews(
 
   ExtensionCustomBindings* v8_extension =
       GetFromArguments<ExtensionCustomBindings>(args);
-  const ::Extension* extension =
+  const Extension* extension =
       v8_extension->GetExtensionForCurrentRenderView();
   if (!extension)
     return v8::Undefined();
diff --git a/chrome/renderer/extensions/extension_dispatcher.cc b/chrome/renderer/extensions/extension_dispatcher.cc
index 9706f67..a070496 100644
--- a/chrome/renderer/extensions/extension_dispatcher.cc
+++ b/chrome/renderer/extensions/extension_dispatcher.cc
@@ -71,6 +71,7 @@ using WebKit::WebView;
 using content::RenderThread;
 using extensions::ApiDefinitionsNatives;
 using extensions::ContextMenusCustomBindings;
+using extensions::Extension;
 using extensions::ExperimentalUsbCustomBindings;
 using extensions::ExtensionAPI;
 using extensions::ExtensionCustomBindings;
@@ -86,6 +87,7 @@ using extensions::SendRequestNatives;
 using extensions::SetIconNatives;
 using extensions::TTSCustomBindings;
 using extensions::TabsCustomBindings;
+using extensions::UpdatedExtensionPermissionsInfo;
 using extensions::WebRequestCustomBindings;
 
 namespace {
diff --git a/chrome/renderer/extensions/extension_dispatcher.h b/chrome/renderer/extensions/extension_dispatcher.h
index 086656f..0bc9647 100644
--- a/chrome/renderer/extensions/extension_dispatcher.h
+++ b/chrome/renderer/extensions/extension_dispatcher.h
@@ -40,6 +40,10 @@ namespace content {
 class RenderThread;
 }
 
+namespace extension {
+class Extension;
+}
+
 // Dispatches extension control messages sent to the renderer and stores
 // renderer extension related state.
 class ExtensionDispatcher : public content::RenderProcessObserver {
@@ -140,7 +144,7 @@ class ExtensionDispatcher : public content::RenderProcessObserver {
       const std::vector<ExtensionMsg_Loaded_Params>& loaded_extensions);
   void OnUnloaded(const std::string& id);
   void OnSetScriptingWhitelist(
-      const Extension::ScriptingWhitelist& extension_ids);
+      const extensions::Extension::ScriptingWhitelist& extension_ids);
   void OnPageActionsUpdated(const std::string& extension_id,
       const std::vector<std::string>& page_actions);
   void OnActivateExtension(const std::string& extension_id);
@@ -165,10 +169,11 @@ class ExtensionDispatcher : public content::RenderProcessObserver {
   void RegisterExtension(v8::Extension* extension, bool restrict_to_extensions);
 
   // Sets up the host permissions for |extension|.
-  void InitOriginPermissions(const Extension* extension);
-  void UpdateOriginPermissions(UpdatedExtensionPermissionsInfo::Reason reason,
-                               const Extension* extension,
-                               const URLPatternSet& origins);
+  void InitOriginPermissions(const extensions::Extension* extension);
+  void UpdateOriginPermissions(
+      extensions::UpdatedExtensionPermissionsInfo::Reason reason,
+      const extensions::Extension* extension,
+      const URLPatternSet& origins);
 
   void RegisterNativeHandlers(ModuleSystem* module_system,
                               ChromeV8Context* context);
diff --git a/chrome/renderer/extensions/extension_resource_request_policy.cc b/chrome/renderer/extensions/extension_resource_request_policy.cc
index 6e62a85..9f1e842 100644
--- a/chrome/renderer/extensions/extension_resource_request_policy.cc
+++ b/chrome/renderer/extensions/extension_resource_request_policy.cc
@@ -17,6 +17,8 @@
 #include "third_party/WebKit/Source/WebKit/chromium/public/WebFrame.h"
 #include "third_party/WebKit/Source/WebKit/chromium/public/platform/WebString.h"
 
+using extensions::Extension;
+
 // static
 bool ExtensionResourceRequestPolicy::CanRequestResource(
     const GURL& resource_url,
diff --git a/chrome/renderer/extensions/page_actions_custom_bindings.cc b/chrome/renderer/extensions/page_actions_custom_bindings.cc
index b6e86ee..276a62a 100644
--- a/chrome/renderer/extensions/page_actions_custom_bindings.cc
+++ b/chrome/renderer/extensions/page_actions_custom_bindings.cc
@@ -26,7 +26,7 @@ v8::Handle<v8::Value> PageActionsCustomBindings::GetCurrentPageActions(
       GetFromArguments<PageActionsCustomBindings>(args);
   std::string extension_id = *v8::String::Utf8Value(args[0]->ToString());
   CHECK(!extension_id.empty());
-  const ::Extension* extension =
+  const Extension* extension =
       self->extension_dispatcher_->extensions()->GetByID(extension_id);
   CHECK(extension);
 
diff --git a/chrome/renderer/extensions/user_script_scheduler.cc b/chrome/renderer/extensions/user_script_scheduler.cc
index 58f3104..916b429 100644
--- a/chrome/renderer/extensions/user_script_scheduler.cc
+++ b/chrome/renderer/extensions/user_script_scheduler.cc
@@ -29,6 +29,7 @@ using WebKit::WebDocument;
 using WebKit::WebFrame;
 using WebKit::WebString;
 using WebKit::WebView;
+using extensions::Extension;
 
 UserScriptScheduler::UserScriptScheduler(
     WebFrame* frame, ExtensionDispatcher* extension_dispatcher)
diff --git a/chrome/renderer/extensions/user_script_slave.cc b/chrome/renderer/extensions/user_script_slave.cc
index 9008381..8c346d5 100644
--- a/chrome/renderer/extensions/user_script_slave.cc
+++ b/chrome/renderer/extensions/user_script_slave.cc
@@ -39,6 +39,7 @@ using WebKit::WebString;
 using WebKit::WebVector;
 using WebKit::WebView;
 using content::RenderThread;
+using extensions::Extension;
 
 // These two strings are injected before and after the Greasemonkey API and
 // user script to wrap it in an anonymous scope.
diff --git a/chrome/renderer/extensions/user_script_slave.h b/chrome/renderer/extensions/user_script_slave.h
index d2f5fec..fad2f42 100644
--- a/chrome/renderer/extensions/user_script_slave.h
+++ b/chrome/renderer/extensions/user_script_slave.h
@@ -18,10 +18,13 @@
 #include "chrome/common/extensions/user_script.h"
 #include "third_party/WebKit/Source/WebKit/chromium/public/WebScriptSource.h"
 
-class Extension;
 class ExtensionSet;
 class GURL;
 
+namespace extensions {
+class Extension;
+}
+
 namespace WebKit {
 class WebFrame;
 }
@@ -52,7 +55,7 @@ class UserScriptSlave {
   // Gets the isolated world ID to use for the given |extension| in the given
   // |frame|. If no isolated world has been created for that extension,
   // one will be created and initialized.
-  int GetIsolatedWorldIdForExtension(const Extension* extension,
+  int GetIsolatedWorldIdForExtension(const extensions::Extension* extension,
                                      WebKit::WebFrame* frame);
 
   // Gets the id of the extension running in a given isolated world. If no such
@@ -64,7 +67,7 @@ class UserScriptSlave {
 
  private:
   static void InitializeIsolatedWorld(int isolated_world_id,
-                                      const Extension* extension);
+                                      const extensions::Extension* extension);
 
   // Shared memory containing raw script data.
   scoped_ptr<base::SharedMemory> shared_memory_;
diff --git a/chrome/renderer/extensions/webstore_bindings.cc b/chrome/renderer/extensions/webstore_bindings.cc
index 7214db9..c234e63 100644
--- a/chrome/renderer/extensions/webstore_bindings.cc
+++ b/chrome/renderer/extensions/webstore_bindings.cc
@@ -173,7 +173,7 @@ bool WebstoreBindings::GetWebstoreItemIdFromFrame(
 
     std::string candidate_webstore_item_id = webstore_url.path().substr(
         webstore_base_url.path().length());
-    if (!::Extension::IdIsValid(candidate_webstore_item_id)) {
+    if (!extensions::Extension::IdIsValid(candidate_webstore_item_id)) {
       *error = kInvalidWebstoreItemUrlError;
       return false;
     }
diff --git a/chrome/renderer/localized_error.cc b/chrome/renderer/localized_error.cc
index 548b77c..430c4af 100644
--- a/chrome/renderer/localized_error.cc
+++ b/chrome/renderer/localized_error.cc
@@ -707,7 +707,7 @@ void LocalizedError::GetFormRepostStrings(const GURL& display_url,
 void LocalizedError::GetAppErrorStrings(
     const WebURLError& error,
     const GURL& display_url,
-    const Extension* app,
+    const extensions::Extension* app,
     DictionaryValue* error_strings) {
   DCHECK(app);
 
diff --git a/chrome/renderer/localized_error.h b/chrome/renderer/localized_error.h
index 1006ae6..0ccf86d 100644
--- a/chrome/renderer/localized_error.h
+++ b/chrome/renderer/localized_error.h
@@ -11,13 +11,16 @@
 #include "base/basictypes.h"
 #include "base/string16.h"
 
-class Extension;
 class GURL;
 
 namespace base {
 class DictionaryValue;
 }
 
+namespace extensions {
+class Extension;
+}
+
 namespace WebKit {
 struct WebURLError;
 }
@@ -48,7 +51,7 @@ class LocalizedError {
   // part of the app.
   static void GetAppErrorStrings(const WebKit::WebURLError& error,
                                  const GURL& display_url,
-                                 const Extension* app,
+                                 const extensions::Extension* app,
                                  base::DictionaryValue* error_strings);
 
   static const char kHttpErrorDomain[];
diff --git a/chrome/test/base/test_browser_window.h b/chrome/test/base/test_browser_window.h
index 3c75b0a..56c7e5d 100644
--- a/chrome/test/base/test_browser_window.h
+++ b/chrome/test/base/test_browser_window.h
@@ -12,6 +12,10 @@
 #include "chrome/browser/ui/browser_window.h"
 #include "chrome/test/base/test_location_bar.h"
 
+namespace extensions {
+class Extension;
+}
+
 // An implementation of BrowserWindow used for testing. TestBrowserWindow only
 // contains a valid LocationBar, all other getters return NULL.
 // See BrowserWithTestWindowTest for an example of using this class.
@@ -75,7 +79,7 @@ class TestBrowserWindow : public BrowserWindow {
       TabContentsWrapper* tab_contents) OVERRIDE {}
   virtual void ShowCreateChromeAppShortcutsDialog(
       Profile* profile,
-      const Extension* app) OVERRIDE {}
+      const extensions::Extension* app) OVERRIDE {}
 
   virtual bool IsBookmarkBarVisible() const OVERRIDE;
   virtual bool IsBookmarkBarAnimating() const OVERRIDE;
diff --git a/chrome/test/base/testing_profile.cc b/chrome/test/base/testing_profile.cc
index 3aa61dc..334728e 100644
--- a/chrome/test/base/testing_profile.cc
+++ b/chrome/test/base/testing_profile.cc
@@ -536,7 +536,7 @@ net::URLRequestContextGetter* TestingProfile::GetRequestContextForRenderProcess(
   ExtensionService* extension_service =
       ExtensionSystem::Get(this)->extension_service();
   if (extension_service) {
-    const Extension* installed_app = extension_service->
+    const extensions::Extension* installed_app = extension_service->
         GetInstalledAppForRenderer(renderer_child_id);
     if (installed_app != NULL && installed_app->is_storage_isolated())
       return GetRequestContextForIsolatedApp(installed_app->id());
diff --git a/chrome/utility/chrome_content_utility_client.cc b/chrome/utility/chrome_content_utility_client.cc
index ade6bd7..7bccbfc 100644
--- a/chrome/utility/chrome_content_utility_client.cc
+++ b/chrome/utility/chrome_content_utility_client.cc
@@ -102,12 +102,12 @@ void ChromeContentUtilityClient::OnUnpackExtension(
     const std::string& extension_id,
     int location,
     int creation_flags) {
-  CHECK(location > Extension::INVALID);
-  CHECK(location < Extension::NUM_LOCATIONS);
+  CHECK(location > extensions::Extension::INVALID);
+  CHECK(location < extensions::Extension::NUM_LOCATIONS);
   ExtensionUnpacker unpacker(
       extension_path,
       extension_id,
-      static_cast<Extension::Location>(location),
+      static_cast<extensions::Extension::Location>(location),
       creation_flags);
   if (unpacker.Run() && unpacker.DumpImagesToFile() &&
       unpacker.DumpMessageCatalogsToFile()) {