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

188 files changed, 706 insertions, 446 deletions

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);