Part 3 of immutable Extension refactor.

Make ExtensionsService hold const Extension pointers only. This ensures that
extensions can't be modified after they're created, and lets us share them
between threads.

BUG=56558
TEST=no functional change

Review URL: http://codereview.chromium.org/4138006

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@64517 0039d316-1c4b-4281-b951-d872f2087c98

159 files changed, 693 insertions, 633 deletions

diff --git a/chrome/browser/app_launched_animation.h b/chrome/browser/app_launched_animation.h
index 278b228..91c029f 100644
--- a/chrome/browser/app_launched_animation.h
+++ b/chrome/browser/app_launched_animation.h
@@ -18,7 +18,7 @@ class AppLaunchedAnimation {
  public:
   // Starts an animation of the |extension| being launched. The |rect| is the
   // rect of the app icon.
-  static void Show(Extension* extension, const gfx::Rect& rect);
+  static void Show(const Extension* extension, const gfx::Rect& rect);
 
  private:
   AppLaunchedAnimation() { }
diff --git a/chrome/browser/autocomplete/keyword_provider.cc b/chrome/browser/autocomplete/keyword_provider.cc
index 8bc133e..3111812 100644
--- a/chrome/browser/autocomplete/keyword_provider.cc
+++ b/chrome/browser/autocomplete/keyword_provider.cc
@@ -186,7 +186,7 @@ void KeywordProvider::Start(const AutocompleteInput& input,
       // If this extension keyword is disabled, make sure we don't add any
       // matches (including the synchronous one below).
       ExtensionsService* service = profile_->GetExtensionsService();
-      Extension* extension = service->GetExtensionById(
+      const Extension* extension = service->GetExtensionById(
           template_url->GetExtensionId(), false);
       bool enabled = extension && (!profile_->IsOffTheRecord() ||
                                    service->IsIncognitoEnabled(extension));
diff --git a/chrome/browser/automation/automation_extension_tracker.cc b/chrome/browser/automation/automation_extension_tracker.cc
index cd816d3..8ab734d 100644
--- a/chrome/browser/automation/automation_extension_tracker.cc
+++ b/chrome/browser/automation/automation_extension_tracker.cc
@@ -10,7 +10,7 @@
 
 AutomationExtensionTracker::AutomationExtensionTracker(
     IPC::Message::Sender* automation)
-    : AutomationResourceTracker<Extension*>(automation) {
+    : AutomationResourceTracker<const Extension*>(automation) {
   registrar_.Add(this, NotificationType::EXTENSION_UNLOADED,
                  NotificationService::AllSources());
   registrar_.Add(this, NotificationType::EXTENSION_UNLOADED_DISABLED,
@@ -20,9 +20,9 @@ AutomationExtensionTracker::AutomationExtensionTracker(
 AutomationExtensionTracker::~AutomationExtensionTracker() {
 }
 
-void AutomationExtensionTracker::AddObserver(Extension* resource) {}
+void AutomationExtensionTracker::AddObserver(const Extension* resource) {}
 
-void AutomationExtensionTracker::RemoveObserver(Extension* resource) {}
+void AutomationExtensionTracker::RemoveObserver(const Extension* resource) {}
 
 void AutomationExtensionTracker::Observe(NotificationType type,
                                          const NotificationSource& source,
@@ -31,7 +31,7 @@ void AutomationExtensionTracker::Observe(NotificationType type,
       type != NotificationType::EXTENSION_UNLOADED_DISABLED)
     return;
 
-  Extension* extension = Details<Extension>(details).ptr();
+  const Extension* extension = Details<const Extension>(details).ptr();
   Profile* profile = Source<Profile>(source).ptr();
   if (profile) {
     ExtensionsService* service = profile->GetExtensionsService();
diff --git a/chrome/browser/automation/automation_extension_tracker.h b/chrome/browser/automation/automation_extension_tracker.h
index c1b7ed7..05f16b5 100644
--- a/chrome/browser/automation/automation_extension_tracker.h
+++ b/chrome/browser/automation/automation_extension_tracker.h
@@ -12,7 +12,7 @@ class Extension;
 
 // Tracks an Extension. An Extension is removed on uninstall, not on disable.
 class AutomationExtensionTracker
-    : public AutomationResourceTracker<Extension*> {
+    : public AutomationResourceTracker<const Extension*> {
  public:
   explicit AutomationExtensionTracker(IPC::Message::Sender* automation);
 
@@ -23,10 +23,10 @@ class AutomationExtensionTracker
   // extension, is the one who sends the notification about extension
   // uninstalls. Instead of using this method, one observer is added for all
   // extensions in the constructor.
-  virtual void AddObserver(Extension* resource);
+  virtual void AddObserver(const Extension* resource);
 
   // See related comment above as to why this method is empty.
-  virtual void RemoveObserver(Extension* resource);
+  virtual void RemoveObserver(const Extension* resource);
 
   // Overriding AutomationResourceTracker Observe. AutomationResourceTracker's
   // Observe expects the NotificationSource to be the object that is closing.
diff --git a/chrome/browser/automation/automation_provider.cc b/chrome/browser/automation/automation_provider.cc
index db4ad51..60ed6ef 100644
--- a/chrome/browser/automation/automation_provider.cc
+++ b/chrome/browser/automation/automation_provider.cc
@@ -258,7 +258,7 @@ int AutomationProvider::GetIndexForNavigationController(
   return parent->GetIndexOfController(controller);
 }
 
-int AutomationProvider::AddExtension(Extension* extension) {
+int AutomationProvider::AddExtension(const Extension* extension) {
   DCHECK(extension);
   return extension_tracker_->Add(extension);
 }
@@ -299,12 +299,13 @@ DictionaryValue* AutomationProvider::GetDictionaryFromDownloadItem(
   return dl_item_value;
 }
 
-Extension* AutomationProvider::GetExtension(int extension_handle) {
+const Extension* AutomationProvider::GetExtension(int extension_handle) {
   return extension_tracker_->GetResource(extension_handle);
 }
 
-Extension* AutomationProvider::GetEnabledExtension(int extension_handle) {
-  Extension* extension = extension_tracker_->GetResource(extension_handle);
+const Extension* AutomationProvider::GetEnabledExtension(int extension_handle) {
+  const Extension* extension =
+      extension_tracker_->GetResource(extension_handle);
   ExtensionsService* service = profile_->GetExtensionsService();
   if (extension && service &&
       service->GetExtensionById(extension->id(), false))
@@ -312,8 +313,10 @@ Extension* AutomationProvider::GetEnabledExtension(int extension_handle) {
   return NULL;
 }
 
-Extension* AutomationProvider::GetDisabledExtension(int extension_handle) {
-  Extension* extension = extension_tracker_->GetResource(extension_handle);
+const Extension* AutomationProvider::GetDisabledExtension(
+    int extension_handle) {
+  const Extension* extension =
+      extension_tracker_->GetResource(extension_handle);
   ExtensionsService* service = profile_->GetExtensionsService();
   if (extension && service &&
       service->GetExtensionById(extension->id(), true) &&
@@ -799,7 +802,7 @@ void AutomationProvider::GetEnabledExtensions(
     const ExtensionList* extensions = service->extensions();
     DCHECK(extensions);
     for (size_t i = 0; i < extensions->size(); ++i) {
-      Extension* extension = (*extensions)[i];
+      const Extension* extension = (*extensions)[i];
       DCHECK(extension);
       if (extension->location() == Extension::INTERNAL ||
           extension->location() == Extension::LOAD) {
@@ -848,7 +851,7 @@ void AutomationProvider::InstallExtensionAndGetHandle(
 void AutomationProvider::UninstallExtension(int extension_handle,
                                             bool* success) {
   *success = false;
-  Extension* extension = GetExtension(extension_handle);
+  const Extension* extension = GetExtension(extension_handle);
   ExtensionsService* service = profile_->GetExtensionsService();
   if (extension && service) {
     ExtensionUnloadNotificationObserver observer;
@@ -861,7 +864,7 @@ void AutomationProvider::UninstallExtension(int extension_handle,
 
 void AutomationProvider::EnableExtension(int extension_handle,
                                          IPC::Message* reply_message) {
-  Extension* extension = GetDisabledExtension(extension_handle);
+  const Extension* extension = GetDisabledExtension(extension_handle);
   ExtensionsService* service = profile_->GetExtensionsService();
   ExtensionProcessManager* manager = profile_->GetExtensionProcessManager();
   // Only enable if this extension is disabled.
@@ -882,7 +885,7 @@ void AutomationProvider::EnableExtension(int extension_handle,
 void AutomationProvider::DisableExtension(int extension_handle,
                                           bool* success) {
   *success = false;
-  Extension* extension = GetEnabledExtension(extension_handle);
+  const Extension* extension = GetEnabledExtension(extension_handle);
   ExtensionsService* service = profile_->GetExtensionsService();
   if (extension && service) {
     ExtensionUnloadNotificationObserver observer;
@@ -897,7 +900,7 @@ void AutomationProvider::ExecuteExtensionActionInActiveTabAsync(
     int extension_handle, int browser_handle,
     IPC::Message* reply_message) {
   bool success = false;
-  Extension* extension = GetEnabledExtension(extension_handle);
+  const Extension* extension = GetEnabledExtension(extension_handle);
   ExtensionsService* service = profile_->GetExtensionsService();
   ExtensionMessageService* message_service =
       profile_->GetExtensionMessageService();
@@ -922,7 +925,7 @@ void AutomationProvider::ExecuteExtensionActionInActiveTabAsync(
 void AutomationProvider::MoveExtensionBrowserAction(
     int extension_handle, int index, bool* success) {
   *success = false;
-  Extension* extension = GetEnabledExtension(extension_handle);
+  const Extension* extension = GetEnabledExtension(extension_handle);
   ExtensionsService* service = profile_->GetExtensionsService();
   if (extension && service) {
     ExtensionToolbarModel* toolbar = service->toolbar_model();
@@ -943,7 +946,7 @@ void AutomationProvider::GetExtensionProperty(
     bool* success,
     std::string* value) {
   *success = false;
-  Extension* extension = GetExtension(extension_handle);
+  const Extension* extension = GetExtension(extension_handle);
   ExtensionsService* service = profile_->GetExtensionsService();
   if (extension && service) {
     ExtensionToolbarModel* toolbar = service->toolbar_model();
diff --git a/chrome/browser/automation/automation_provider.h b/chrome/browser/automation/automation_provider.h
index 5a29b04..66d084a 100644
--- a/chrome/browser/automation/automation_provider.h
+++ b/chrome/browser/automation/automation_provider.h
@@ -150,7 +150,7 @@ class AutomationProvider : public base::RefCounted<AutomationProvider>,
   // Adds the extension passed in to the extension tracker, and returns
   // the associated handle. If the tracker already contains the extension,
   // the handle is simply returned.
-  int AddExtension(Extension* extension);
+  int AddExtension(const Extension* extension);
 
 #if defined(OS_WIN)
   // Adds the external tab passed in to the tab tracker.
@@ -323,15 +323,15 @@ class AutomationProvider : public base::RefCounted<AutomationProvider>,
 
   // Returns the extension for the given handle. Returns NULL if there is
   // no extension for the handle.
-  Extension* GetExtension(int extension_handle);
+  const Extension* GetExtension(int extension_handle);
 
   // Returns the extension for the given handle, if the handle is valid and
   // the associated extension is enabled. Returns NULL otherwise.
-  Extension* GetEnabledExtension(int extension_handle);
+  const Extension* GetEnabledExtension(int extension_handle);
 
   // Returns the extension for the given handle, if the handle is valid and
   // the associated extension is disabled. Returns NULL otherwise.
-  Extension* GetDisabledExtension(int extension_handle);
+  const Extension* GetDisabledExtension(int extension_handle);
 
   // Method called by the popup menu tracker when a popup menu is opened.
   void NotifyPopupMenuOpened();
diff --git a/chrome/browser/automation/automation_provider_observers.cc b/chrome/browser/automation/automation_provider_observers.cc
index aeabd00..7cfa96f 100644
--- a/chrome/browser/automation/automation_provider_observers.cc
+++ b/chrome/browser/automation/automation_provider_observers.cc
@@ -494,7 +494,7 @@ void ExtensionReadyNotificationObserver::Observe(
       success = true;
       break;
     case NotificationType::EXTENSION_LOADED:
-      extension_ = Details<Extension>(details).ptr();
+      extension_ = Details<const Extension>(details).ptr();
       if (!DidExtensionHostsStopLoading(manager_))
         return;
       success = true;
diff --git a/chrome/browser/automation/automation_provider_observers.h b/chrome/browser/automation/automation_provider_observers.h
index de20990..7b76638 100644
--- a/chrome/browser/automation/automation_provider_observers.h
+++ b/chrome/browser/automation/automation_provider_observers.h
@@ -273,7 +273,7 @@ class ExtensionReadyNotificationObserver : public NotificationObserver {
   scoped_refptr<AutomationProvider> automation_;
   int id_;
   IPC::Message* reply_message_;
-  Extension* extension_;
+  const Extension* extension_;
 
   DISALLOW_COPY_AND_ASSIGN(ExtensionReadyNotificationObserver);
 };
diff --git a/chrome/browser/automation/automation_resource_tracker.cc b/chrome/browser/automation/automation_resource_tracker.cc
index c233b41..a82265d 100644
--- a/chrome/browser/automation/automation_resource_tracker.cc
+++ b/chrome/browser/automation/automation_resource_tracker.cc
@@ -15,7 +15,7 @@ AutomationResourceTrackerImpl::AutomationResourceTrackerImpl(
 AutomationResourceTrackerImpl::~AutomationResourceTrackerImpl() {
 }
 
-int AutomationResourceTrackerImpl::AddImpl(void* resource) {
+int AutomationResourceTrackerImpl::AddImpl(const void* resource) {
   if (ContainsResourceImpl(resource))
     return resource_to_handle_[resource];
 
@@ -30,7 +30,7 @@ int AutomationResourceTrackerImpl::AddImpl(void* resource) {
   return handle;
 }
 
-void AutomationResourceTrackerImpl::RemoveImpl(void* resource) {
+void AutomationResourceTrackerImpl::RemoveImpl(const void* resource) {
   if (!ContainsResourceImpl(resource))
     return;
 
@@ -48,7 +48,7 @@ int AutomationResourceTrackerImpl::GenerateHandle() {
   return ++handle;
 }
 
-bool AutomationResourceTrackerImpl::ContainsResourceImpl(void* resource) {
+bool AutomationResourceTrackerImpl::ContainsResourceImpl(const void* resource) {
   return resource_to_handle_.find(resource) != resource_to_handle_.end();
 }
 
@@ -56,7 +56,7 @@ bool AutomationResourceTrackerImpl::ContainsHandleImpl(int handle) {
   return handle_to_resource_.find(handle) != handle_to_resource_.end();
 }
 
-void* AutomationResourceTrackerImpl::GetResourceImpl(int handle) {
+const void* AutomationResourceTrackerImpl::GetResourceImpl(int handle) {
   HandleToResourceMap::const_iterator iter = handle_to_resource_.find(handle);
   if (iter == handle_to_resource_.end())
     return NULL;
@@ -64,7 +64,7 @@ void* AutomationResourceTrackerImpl::GetResourceImpl(int handle) {
   return iter->second;
 }
 
-int AutomationResourceTrackerImpl::GetHandleImpl(void* resource) {
+int AutomationResourceTrackerImpl::GetHandleImpl(const void* resource) {
   ResourceToHandleMap::const_iterator iter =
     resource_to_handle_.find(resource);
   if (iter == resource_to_handle_.end())
@@ -73,7 +73,8 @@ int AutomationResourceTrackerImpl::GetHandleImpl(void* resource) {
   return iter->second;
 }
 
-void AutomationResourceTrackerImpl::HandleCloseNotification(void* resource) {
+void AutomationResourceTrackerImpl::HandleCloseNotification(
+    const void* resource) {
   if (!ContainsResourceImpl(resource))
     return;
 
diff --git a/chrome/browser/automation/automation_resource_tracker.h b/chrome/browser/automation/automation_resource_tracker.h
index 671f72b..2d6b0cd 100644
--- a/chrome/browser/automation/automation_resource_tracker.h
+++ b/chrome/browser/automation/automation_resource_tracker.h
@@ -38,21 +38,21 @@ class AutomationResourceTrackerImpl {
   // These need to be implemented in AutomationResourceTracker,
   // since it needs to call the subclass's type-specific notification
   // registration functions.
-  virtual void AddObserverTypeProxy(void* resource) = 0;
-  virtual void RemoveObserverTypeProxy(void* resource) = 0;
+  virtual void AddObserverTypeProxy(const void* resource) = 0;
+  virtual void RemoveObserverTypeProxy(const void* resource) = 0;
 
-  int AddImpl(void* resource);
-  void RemoveImpl(void* resource);
+  int AddImpl(const void* resource);
+  void RemoveImpl(const void* resource);
   int GenerateHandle();
-  bool ContainsResourceImpl(void* resource);
+  bool ContainsResourceImpl(const void* resource);
   bool ContainsHandleImpl(int handle);
-  void* GetResourceImpl(int handle);
-  int GetHandleImpl(void* resource);
-  void HandleCloseNotification(void* resource);
+  const void* GetResourceImpl(int handle);
+  int GetHandleImpl(const void* resource);
+  void HandleCloseNotification(const void* resource);
 
  protected:
-  typedef std::map<void*, int> ResourceToHandleMap;
-  typedef std::map<int, void*> HandleToResourceMap;
+  typedef std::map<const void*, int> ResourceToHandleMap;
+  typedef std::map<int, const void*> HandleToResourceMap;
   ResourceToHandleMap resource_to_handle_;
   HandleToResourceMap handle_to_resource_;
 
@@ -109,8 +109,9 @@ class AutomationResourceTracker : public NotificationObserver,
 
   // Returns the resource pointer associated with a given handle, or NULL
   // if that handle is not present in the mapping.
+  // The casts here allow this to compile with both T = Foo and T = const Foo.
   T GetResource(int handle) {
-    return static_cast<T>(GetResourceImpl(handle));
+    return static_cast<T>(const_cast<void*>(GetResourceImpl(handle)));
   }
 
   // Returns the handle associated with a given resource pointer, or 0 if
@@ -144,11 +145,12 @@ class AutomationResourceTracker : public NotificationObserver,
 
  private:
   // These proxy calls from the base Impl class to the template's subclss.
-  virtual void AddObserverTypeProxy(void* resource) {
-    AddObserver(static_cast<T>(resource));
+  // The casts here allow this to compile with both T = Foo and T = const Foo.
+  virtual void AddObserverTypeProxy(const void* resource) {
+    AddObserver(static_cast<T>(const_cast<void*>(resource)));
   }
-  virtual void RemoveObserverTypeProxy(void* resource) {
-    RemoveObserver(static_cast<T>(resource));
+  virtual void RemoveObserverTypeProxy(const void* resource) {
+    RemoveObserver(static_cast<T>(const_cast<void*>(resource)));
   }
 
   DISALLOW_COPY_AND_ASSIGN(AutomationResourceTracker);
diff --git a/chrome/browser/automation/testing_automation_provider.cc b/chrome/browser/automation/testing_automation_provider.cc
index 8f648d0..ec10dfa 100644
--- a/chrome/browser/automation/testing_automation_provider.cc
+++ b/chrome/browser/automation/testing_automation_provider.cc
@@ -3672,7 +3672,7 @@ void TestingAutomationProvider::GetThemeInfo(
     DictionaryValue* args,
     IPC::Message* reply_message) {
   scoped_ptr<DictionaryValue> return_value(new DictionaryValue);
-  Extension* theme = browser->profile()->GetTheme();
+  const Extension* theme = browser->profile()->GetTheme();
   if (theme) {
     return_value->SetString("name", theme->name());
     return_value->Set("images", theme->GetThemeImages()->DeepCopy());
diff --git a/chrome/browser/background_contents_service.cc b/chrome/browser/background_contents_service.cc
index 1c9b71e..8517d97 100644
--- a/chrome/browser/background_contents_service.cc
+++ b/chrome/browser/background_contents_service.cc
@@ -110,7 +110,7 @@ void BackgroundContentsService::Observe(NotificationType type,
       break;
     case NotificationType::EXTENSION_UNLOADED:
       ShutdownAssociatedBackgroundContents(
-          ASCIIToUTF16(Details<Extension>(details)->id()));
+          ASCIIToUTF16(Details<const Extension>(details)->id()));
       break;
     default:
       NOTREACHED();
@@ -157,7 +157,7 @@ void BackgroundContentsService::CreateBackgroundContents(
 
   // Check to make sure that the parent extension is still enabled.
   ExtensionsService* extensions_service = profile->GetExtensionsService();
-  Extension* extension = extensions_service->GetExtensionById(
+  const Extension* extension = extensions_service->GetExtensionById(
       UTF16ToASCII(application_id), false);
 
   if (!extension) {
diff --git a/chrome/browser/background_mode_manager.cc b/chrome/browser/background_mode_manager.cc
index 080e3b2..0fc898f 100644
--- a/chrome/browser/background_mode_manager.cc
+++ b/chrome/browser/background_mode_manager.cc
@@ -239,15 +239,15 @@ void BackgroundModeManager::Observe(NotificationType type,
 #endif
       break;
     case NotificationType::EXTENSION_LOADED:
-      if (IsBackgroundApp(*Details<Extension>(details).ptr()))
+      if (IsBackgroundApp(*Details<const Extension>(details).ptr()))
         OnBackgroundAppLoaded();
       break;
     case NotificationType::EXTENSION_UNLOADED:
-      if (IsBackgroundApp(*Details<Extension>(details).ptr()))
+      if (IsBackgroundApp(*Details<const Extension>(details).ptr()))
         OnBackgroundAppUnloaded();
       break;
     case NotificationType::EXTENSION_INSTALLED:
-      if (IsBackgroundApp(*Details<Extension>(details).ptr()))
+      if (IsBackgroundApp(*Details<const Extension>(details).ptr()))
         OnBackgroundAppInstalled();
       break;
     case NotificationType::EXTENSION_UNINSTALLED:
diff --git a/chrome/browser/browser.cc b/chrome/browser/browser.cc
index 12d2338..7c1c05a 100644
--- a/chrome/browser/browser.cc
+++ b/chrome/browser/browser.cc
@@ -345,7 +345,7 @@ Browser* Browser::CreateForType(Type type, Profile* profile) {
 
 // static
 Browser* Browser::CreateForApp(const std::string& app_name,
-                               Extension* extension,
+                               const Extension* extension,
                                Profile* profile,
                                bool is_panel) {
   Browser::Type type = TYPE_APP;
@@ -499,7 +499,8 @@ TabContents* Browser::OpenApplication(Profile* profile,
 
   // If the extension with |app_id| could't be found, most likely because it
   // was uninstalled.
-  Extension* extension = extensions_service->GetExtensionById(app_id, false);
+  const Extension* extension =
+      extensions_service->GetExtensionById(app_id, false);
   if (!extension)
     return NULL;
 
@@ -510,7 +511,7 @@ TabContents* Browser::OpenApplication(Profile* profile,
 // static
 TabContents* Browser::OpenApplication(
     Profile* profile,
-    Extension* extension,
+    const Extension* extension,
     extension_misc::LaunchContainer container,
     TabContents* existing_tab) {
   TabContents* tab = NULL;
@@ -538,7 +539,7 @@ TabContents* Browser::OpenApplication(
 // static
 TabContents* Browser::OpenApplicationWindow(
     Profile* profile,
-    Extension* extension,
+    const Extension* extension,
     extension_misc::LaunchContainer container,
     const GURL& url_input) {
   GURL url;
@@ -589,7 +590,7 @@ TabContents* Browser::OpenApplicationWindow(Profile* profile, GURL& url) {
 
 // static
 TabContents* Browser::OpenApplicationTab(Profile* profile,
-                                         Extension* extension,
+                                         const Extension* extension,
                                          TabContents* existing_tab) {
   Browser* browser = BrowserList::GetLastActiveWithProfile(profile);
   TabContents* contents = NULL;
@@ -3273,7 +3274,7 @@ void Browser::Observe(NotificationType type,
       if (profile_->IsSameProfile(profile)) {
         ExtensionsService* service = profile->GetExtensionsService();
         DCHECK(service);
-        Extension* extension = Details<Extension>(details).ptr();
+        const Extension* extension = Details<const Extension>(details).ptr();
         if (service->extension_prefs()->DidExtensionEscalatePermissions(
                 extension->id()))
           ShowExtensionDisabledUI(service, profile_, extension);
@@ -3286,7 +3287,7 @@ void Browser::Observe(NotificationType type,
       window()->GetLocationBar()->UpdatePageActions();
 
       // Close any tabs from the unloaded extension.
-      Extension* extension = Details<Extension>(details).ptr();
+      const Extension* extension = Details<const Extension>(details).ptr();
       TabStripModel* model = tab_handler_->GetTabStripModel();
       for (int i = model->count() - 1; i >= 0; --i) {
         TabContents* tc = model->GetTabContentsAt(i);
@@ -3322,7 +3323,7 @@ void Browser::Observe(NotificationType type,
       TabContents* tab_contents = GetSelectedTabContents();
       if (!tab_contents)
         break;
-      Extension* extension = Details<Extension>(details).ptr();
+      const Extension* extension = Details<const Extension>(details).ptr();
       CrashedExtensionInfoBarDelegate* delegate = NULL;
       for (int i = 0; i < tab_contents->infobar_delegate_count();) {
         delegate = tab_contents->GetInfoBarDelegateAt(i)->
diff --git a/chrome/browser/browser.h b/chrome/browser/browser.h
index f0e8783..5654106 100644
--- a/chrome/browser/browser.h
+++ b/chrome/browser/browser.h
@@ -145,7 +145,7 @@ class Browser : public TabHandlerDelegate,
   // shell.  |extension| is optional. If supplied, we create a window with
   // a bigger icon and title text, that supports tabs.
   static Browser* CreateForApp(const std::string& app_name,
-                               Extension* extension,
+                               const Extension* extension,
                                Profile* profile,
                                bool is_panel);
 
@@ -154,7 +154,7 @@ class Browser : public TabHandlerDelegate,
   static Browser* CreateForDevTools(Profile* profile);
 
   // Returns the extension app associated with this window, if any.
-  Extension* extension_app() { return extension_app_; }
+  const Extension* extension_app() { return extension_app_; }
 
   // Set overrides for the initial window bounds and maximized state.
   void set_override_bounds(const gfx::Rect& bounds) {
@@ -235,7 +235,7 @@ class Browser : public TabHandlerDelegate,
   // NULL.
   static TabContents* OpenApplication(
       Profile* profile,
-      Extension* extension,
+      const Extension* extension,
       extension_misc::LaunchContainer container,
       TabContents* existing_tab);
 
@@ -246,7 +246,7 @@ class Browser : public TabHandlerDelegate,
   // Browser::Type::EXTENSION_APP (if |extension| is non-NULL).
   static TabContents* OpenApplicationWindow(
       Profile* profile,
-      Extension* extension,
+      const Extension* extension,
       extension_misc::LaunchContainer container,
       const GURL& url);
 
@@ -257,7 +257,7 @@ class Browser : public TabHandlerDelegate,
   // |existing_tab| if not NULL.  Returns NULL if there are no appropriate
   // existing browser windows for |profile|.
   static TabContents* OpenApplicationTab(Profile* profile,
-                                         Extension* extension,
+                                         const Extension* extension,
                                          TabContents* existing_tab);
 
   // Opens a new window and opens the bookmark manager.
@@ -1124,7 +1124,7 @@ class Browser : public TabHandlerDelegate,
   WebAppAction pending_web_app_action_;
 
   // The extension app associated with this window, if any.
-  Extension* extension_app_;
+  const Extension* extension_app_;
 
   // Tracks the display mode of the tabstrip.
   mutable BooleanPrefMember use_vertical_tabs_;
diff --git a/chrome/browser/browser_browsertest.cc b/chrome/browser/browser_browsertest.cc
index 5f2e1e9..6c57f93 100644
--- a/chrome/browser/browser_browsertest.cc
+++ b/chrome/browser/browser_browsertest.cc
@@ -156,7 +156,7 @@ class BrowserTest : public ExtensionBrowserTest {
   }
 
   // Returns the app extension aptly named "App Test".
-  Extension* GetExtension() {
+  const Extension* GetExtension() {
     const ExtensionList* extensions =
         browser()->profile()->GetExtensionsService()->extensions();
     for (size_t i = 0; i < extensions->size(); ++i) {
@@ -426,7 +426,7 @@ IN_PROC_BROWSER_TEST_F(BrowserTest, TabClosingWhenRemovingExtension) {
 
   ASSERT_TRUE(LoadExtension(test_data_dir_.AppendASCII("app/")));
 
-  Extension* extension_app = GetExtension();
+  const Extension* extension_app = GetExtension();
 
   ui_test_utils::NavigateToURL(browser(), url);
 
@@ -509,7 +509,7 @@ IN_PROC_BROWSER_TEST_F(BrowserTest, RestorePinnedTabs) {
   GURL url(test_server()->GetURL("empty.html"));
   TabStripModel* model = browser()->tabstrip_model();
   ASSERT_TRUE(LoadExtension(test_data_dir_.AppendASCII("app/")));
-  Extension* extension_app = GetExtension();
+  const Extension* extension_app = GetExtension();
   ui_test_utils::NavigateToURL(browser(), url);
   TabContents* app_contents = new TabContents(browser()->profile(), NULL,
                                               MSG_ROUTING_NONE, NULL, NULL);
diff --git a/chrome/browser/cocoa/extension_install_prompt.mm b/chrome/browser/cocoa/extension_install_prompt.mm
index cb33136..3306806 100644
--- a/chrome/browser/cocoa/extension_install_prompt.mm
+++ b/chrome/browser/cocoa/extension_install_prompt.mm
@@ -20,7 +20,10 @@
 class Profile;
 
 void ExtensionInstallUI::ShowExtensionInstallUIPromptImpl(
-    Profile* profile, Delegate* delegate, Extension* extension, SkBitmap* icon,
+    Profile* profile,
+    Delegate* delegate,
+    const Extension* extension,
+    SkBitmap* icon,
     ExtensionInstallUI::PromptType type) {
   NSAlert* alert = [[[NSAlert alloc] init] autorelease];
 
diff --git a/chrome/browser/cocoa/extension_installed_bubble_bridge.h b/chrome/browser/cocoa/extension_installed_bubble_bridge.h
index 999fd0a..d878d70 100644
--- a/chrome/browser/cocoa/extension_installed_bubble_bridge.h
+++ b/chrome/browser/cocoa/extension_installed_bubble_bridge.h
@@ -20,7 +20,7 @@ namespace ExtensionInstalledBubbleCocoa {
 // This function is called by the ExtensionInstallUI when an extension has been
 // installed.
 void ShowExtensionInstalledBubble(gfx::NativeWindow window,
-                                  Extension* extension,
+                                  const Extension* extension,
                                   Browser* browser,
                                   SkBitmap icon);
 }
diff --git a/chrome/browser/cocoa/extension_installed_bubble_bridge.mm b/chrome/browser/cocoa/extension_installed_bubble_bridge.mm
index e43b956..9c15e97 100644
--- a/chrome/browser/cocoa/extension_installed_bubble_bridge.mm
+++ b/chrome/browser/cocoa/extension_installed_bubble_bridge.mm
@@ -12,7 +12,7 @@
 
 void ExtensionInstalledBubbleCocoa::ShowExtensionInstalledBubble(
     gfx::NativeWindow window,
-    Extension* extension,
+    const Extension* extension,
     Browser* browser,
     SkBitmap icon) {
   // The controller is deallocated when the window is closed, so no need to
diff --git a/chrome/browser/cocoa/extension_installed_bubble_controller.h b/chrome/browser/cocoa/extension_installed_bubble_controller.h
index bec656d..e5f50a3 100644
--- a/chrome/browser/cocoa/extension_installed_bubble_controller.h
+++ b/chrome/browser/cocoa/extension_installed_bubble_controller.h
@@ -47,7 +47,7 @@ typedef enum {
     NSWindowController<NSWindowDelegate> {
  @private
   NSWindow* parentWindow_;  // weak
-  Extension* extension_;  // weak
+  const Extension* extension_;  // weak
   Browser* browser_;  // weak
   scoped_nsobject<NSImage> icon_;
 
@@ -72,13 +72,13 @@ typedef enum {
   IBOutlet NSTextField* extensionInstalledInfoMsg_;
 }
 
-@property (nonatomic, readonly) Extension* extension;
+@property (nonatomic, readonly) const Extension* extension;
 @property (nonatomic) BOOL pageActionRemoved;
 
 // Initialize the window, and then create observers to wait for the extension
 // to complete loading, or the browser window to close.
 - (id)initWithParentWindow:(NSWindow*)parentWindow
-                 extension:(Extension*)extension
+                 extension:(const Extension*)extension
                    browser:(Browser*)browser
                       icon:(SkBitmap)icon;
 
diff --git a/chrome/browser/cocoa/extension_installed_bubble_controller.mm b/chrome/browser/cocoa/extension_installed_bubble_controller.mm
index b83b303..b1263fd 100644
--- a/chrome/browser/cocoa/extension_installed_bubble_controller.mm
+++ b/chrome/browser/cocoa/extension_installed_bubble_controller.mm
@@ -46,7 +46,7 @@ class ExtensionLoadedNotificationObserver : public NotificationObserver {
                const NotificationSource& source,
                const NotificationDetails& details) {
     if (type == NotificationType::EXTENSION_LOADED) {
-      Extension* extension = Details<Extension>(details).ptr();
+      const Extension* extension = Details<const Extension>(details).ptr();
       if (extension == [controller_ extension]) {
         [controller_ performSelectorOnMainThread:@selector(showWindow:)
                                       withObject:controller_
@@ -74,7 +74,7 @@ class ExtensionLoadedNotificationObserver : public NotificationObserver {
 @synthesize pageActionRemoved = pageActionRemoved_;  // Exposed for unit test.
 
 - (id)initWithParentWindow:(NSWindow*)parentWindow
-                 extension:(Extension*)extension
+                 extension:(const Extension*)extension
                    browser:(Browser*)browser
                       icon:(SkBitmap)icon {
   NSString* nibPath =
diff --git a/chrome/browser/cocoa/extensions/browser_action_button.h b/chrome/browser/cocoa/extensions/browser_action_button.h
index 606b033..1205c80 100644
--- a/chrome/browser/cocoa/extensions/browser_action_button.h
+++ b/chrome/browser/cocoa/extensions/browser_action_button.h
@@ -42,7 +42,7 @@ extern NSString* const kBrowserActionButtonDragEndNotification;
   scoped_nsobject<NSViewAnimation> moveAnimation_;
 
   // The extension for this button. Weak.
-  Extension* extension_;
+  const Extension* extension_;
 
   // The ID of the active tab.
   int tabId_;
@@ -57,7 +57,7 @@ extern NSString* const kBrowserActionButtonDragEndNotification;
 }
 
 - (id)initWithFrame:(NSRect)frame
-          extension:(Extension*)extension
+          extension:(const Extension*)extension
             profile:(Profile*)profile
               tabId:(int)tabId;
 
@@ -76,7 +76,7 @@ extern NSString* const kBrowserActionButtonDragEndNotification;
 - (NSImage*)compositedImage;
 
 @property(readonly, nonatomic) BOOL isBeingDragged;
-@property(readonly, nonatomic) Extension* extension;
+@property(readonly, nonatomic) const Extension* extension;
 @property(readwrite, nonatomic) int tabId;
 
 @end
diff --git a/chrome/browser/cocoa/extensions/browser_action_button.mm b/chrome/browser/cocoa/extensions/browser_action_button.mm
index 70f15ee..0cdaee5 100644
--- a/chrome/browser/cocoa/extensions/browser_action_button.mm
+++ b/chrome/browser/cocoa/extensions/browser_action_button.mm
@@ -45,7 +45,8 @@ const CGFloat kShadowOffset = 2.0;
 class ExtensionImageTrackerBridge : public NotificationObserver,
                                     public ImageLoadingTracker::Observer {
  public:
-  ExtensionImageTrackerBridge(BrowserActionButton* owner, Extension* extension)
+  ExtensionImageTrackerBridge(BrowserActionButton* owner,
+                              const Extension* extension)
       : owner_(owner),
         tracker_(this) {
     // The Browser Action API does not allow the default icon path to be
@@ -113,7 +114,7 @@ class ExtensionImageTrackerBridge : public NotificationObserver,
 }
 
 - (id)initWithFrame:(NSRect)frame
-          extension:(Extension*)extension
+          extension:(const Extension*)extension
             profile:(Profile*)profile
               tabId:(int)tabId {
   if ((self = [super initWithFrame:frame])) {
diff --git a/chrome/browser/cocoa/extensions/browser_actions_controller.h b/chrome/browser/cocoa/extensions/browser_actions_controller.h
index 21b0b95..8f039ce 100644
--- a/chrome/browser/cocoa/extensions/browser_actions_controller.h
+++ b/chrome/browser/cocoa/extensions/browser_actions_controller.h
@@ -88,7 +88,7 @@ extern NSString* const kBrowserActionVisibilityChangedNotification;
 - (void)resizeContainerAndAnimate:(BOOL)animate;
 
 // Returns the NSView for the action button associated with an extension.
-- (NSView*)browserActionViewForExtension:(Extension*)extension;
+- (NSView*)browserActionViewForExtension:(const Extension*)extension;
 
 // Returns the saved width determined by the number of shown Browser Actions
 // preference property. If no preference is found, then the width for the
@@ -98,7 +98,7 @@ extern NSString* const kBrowserActionVisibilityChangedNotification;
 // Returns where the popup arrow should point to for a given Browser Action. If
 // it is passed an extension that is not a Browser Action, then it will return
 // NSZeroPoint.
-- (NSPoint)popupPointForBrowserAction:(Extension*)extension;
+- (NSPoint)popupPointForBrowserAction:(const Extension*)extension;
 
 // Returns whether the chevron button is currently hidden or in the process of
 // being hidden (fading out). Will return NO if it is not hidden or is in the
diff --git a/chrome/browser/cocoa/extensions/browser_actions_controller.mm b/chrome/browser/cocoa/extensions/browser_actions_controller.mm
index e5a58ad..456ceba 100644
--- a/chrome/browser/cocoa/extensions/browser_actions_controller.mm
+++ b/chrome/browser/cocoa/extensions/browser_actions_controller.mm
@@ -70,13 +70,13 @@ const CGFloat kBrowserActionBubbleYOffset = 3.0;
 // Creates and then adds the given extension's action button to the container
 // at the given index within the container. It does not affect the toolbar model
 // object since it is called when the toolbar model changes.
-- (void)createActionButtonForExtension:(Extension*)extension
+- (void)createActionButtonForExtension:(const Extension*)extension
                              withIndex:(NSUInteger)index;
 
 // Removes an action button for the given extension from the container. This
 // method also does not affect the underlying toolbar model since it is called
 // when the toolbar model changes.
-- (void)removeActionButtonForExtension:(Extension*)extension;
+- (void)removeActionButtonForExtension:(const Extension*)extension;
 
 // Useful in the case of a Browser Action being added/removed from the middle of
 // the container, this method repositions each button according to the current
@@ -90,7 +90,7 @@ const CGFloat kBrowserActionBubbleYOffset = 3.0;
 
 // Returns the existing button with the given extension backing it; nil if it
 // cannot be found or the extension's ID is invalid.
-- (BrowserActionButton*)buttonForExtension:(Extension*)extension;
+- (BrowserActionButton*)buttonForExtension:(const Extension*)extension;
 
 // Returns the preferred width of the container given the number of visible
 // buttons |buttonCount|.
@@ -141,7 +141,7 @@ const CGFloat kBrowserActionBubbleYOffset = 3.0;
 
 // Returns whether the given extension should be displayed. Only displays
 // incognito-enabled extensions in incognito mode. Otherwise returns YES.
-- (BOOL)shouldDisplayBrowserAction:(Extension*)extension;
+- (BOOL)shouldDisplayBrowserAction:(const Extension*)extension;
 
 // The reason |frame| is specified in these chevron functions is because the
 // container may be animating and the end frame of the animation should be
@@ -203,12 +203,12 @@ class ExtensionsServiceObserverBridge : public NotificationObserver,
   }
 
   // ExtensionToolbarModel::Observer implementation.
-  void BrowserActionAdded(Extension* extension, int index) {
+  void BrowserActionAdded(const Extension* extension, int index) {
     [owner_ createActionButtonForExtension:extension withIndex:index];
     [owner_ resizeContainerAndAnimate:NO];
   }
 
-  void BrowserActionRemoved(Extension* extension) {
+  void BrowserActionRemoved(const Extension* extension) {
     [owner_ removeActionButtonForExtension:extension];
     [owner_ resizeContainerAndAnimate:NO];
   }
@@ -342,7 +342,7 @@ class ExtensionsServiceObserverBridge : public NotificationObserver,
   }
 }
 
-- (NSView*)browserActionViewForExtension:(Extension*)extension {
+- (NSView*)browserActionViewForExtension:(const Extension*)extension {
   for (BrowserActionButton* button in [buttons_ allValues]) {
     if ([button extension] == extension)
       return button;
@@ -374,7 +374,7 @@ class ExtensionsServiceObserverBridge : public NotificationObserver,
   return [self containerWidthWithButtonCount:savedButtonCount];
 }
 
-- (NSPoint)popupPointForBrowserAction:(Extension*)extension {
+- (NSPoint)popupPointForBrowserAction:(const Extension*)extension {
   if (!extension->browser_action())
     return NSZeroPoint;
 
@@ -446,7 +446,7 @@ class ExtensionsServiceObserverBridge : public NotificationObserver,
   [containerView_ resizeToWidth:width animate:NO];
 }
 
-- (void)createActionButtonForExtension:(Extension*)extension
+- (void)createActionButtonForExtension:(const Extension*)extension
                              withIndex:(NSUInteger)index {
   if (!extension->browser_action())
     return;
@@ -491,7 +491,7 @@ class ExtensionsServiceObserverBridge : public NotificationObserver,
   [containerView_ setNeedsDisplay:YES];
 }
 
-- (void)removeActionButtonForExtension:(Extension*)extension {
+- (void)removeActionButtonForExtension:(const Extension*)extension {
   if (!extension->browser_action())
     return;
 
@@ -555,7 +555,7 @@ class ExtensionsServiceObserverBridge : public NotificationObserver,
   }
 }
 
-- (BrowserActionButton*)buttonForExtension:(Extension*)extension {
+- (BrowserActionButton*)buttonForExtension:(const Extension*)extension {
   NSString* extensionId = base::SysUTF8ToNSString(extension->id());
   DCHECK(extensionId);
   if (!extensionId)
@@ -744,7 +744,7 @@ class ExtensionsServiceObserverBridge : public NotificationObserver,
   }
 }
 
-- (BOOL)shouldDisplayBrowserAction:(Extension*)extension {
+- (BOOL)shouldDisplayBrowserAction:(const Extension*)extension {
   // Only display incognito-enabled extensions while in incognito mode.
   return (!profile_->IsOffTheRecord() ||
           profile_->GetExtensionsService()->IsIncognitoEnabled(extension));
@@ -854,7 +854,7 @@ class ExtensionsServiceObserverBridge : public NotificationObserver,
   if (profile_->IsOffTheRecord())
     index = toolbarModel_->IncognitoIndexToOriginal(index);
   if (index < toolbarModel_->size()) {
-    Extension* extension = toolbarModel_->GetExtensionByIndex(index);
+    const Extension* extension = toolbarModel_->GetExtensionByIndex(index);
     return [buttons_ objectForKey:base::SysUTF8ToNSString(extension->id())];
   }
   return nil;
diff --git a/chrome/browser/cocoa/extensions/extension_action_context_menu.h b/chrome/browser/cocoa/extensions/extension_action_context_menu.h
index 3c9e216..80e8398 100644
--- a/chrome/browser/cocoa/extensions/extension_action_context_menu.h
+++ b/chrome/browser/cocoa/extensions/extension_action_context_menu.h
@@ -28,7 +28,7 @@ class DevmodeObserver;
 @interface ExtensionActionContextMenu : NSMenu {
  @private
   // The extension that this menu belongs to. Weak.
-  Extension* extension_;
+  const Extension* extension_;
 
   // The extension action this menu belongs to. Weak.
   ExtensionAction* action_;
@@ -48,7 +48,7 @@ class DevmodeObserver;
 }
 
 // Initializes and returns a context menu for the given extension and profile.
-- (id)initWithExtension:(Extension*)extension
+- (id)initWithExtension:(const Extension*)extension
                 profile:(Profile*)profile
         extensionAction:(ExtensionAction*)action;
 
diff --git a/chrome/browser/cocoa/extensions/extension_action_context_menu.mm b/chrome/browser/cocoa/extensions/extension_action_context_menu.mm
index 81aa61e..36ff520 100644
--- a/chrome/browser/cocoa/extensions/extension_action_context_menu.mm
+++ b/chrome/browser/cocoa/extensions/extension_action_context_menu.mm
@@ -36,7 +36,7 @@
 // Also acts as the extension's UI delegate in order to display the dialog.
 class AsyncUninstaller : public ExtensionInstallUI::Delegate {
  public:
-  AsyncUninstaller(Extension* extension, Profile* profile)
+  AsyncUninstaller(const Extension* extension, Profile* profile)
       : extension_(extension),
         profile_(profile) {
     install_ui_.reset(new ExtensionInstallUI(profile));
@@ -55,7 +55,7 @@ class AsyncUninstaller : public ExtensionInstallUI::Delegate {
 
  private:
   // The extension that we're loading the icon for. Weak.
-  Extension* extension_;
+  const Extension* extension_;
 
   // The current profile. Weak.
   Profile* profile_;
@@ -125,7 +125,7 @@ int CurrentTabId() {
 
 }  // namespace
 
-- (id)initWithExtension:(Extension*)extension
+- (id)initWithExtension:(const Extension*)extension
                 profile:(Profile*)profile
         extensionAction:(ExtensionAction*)action{
   if ((self = [super initWithTitle:@""])) {
diff --git a/chrome/browser/cocoa/extensions/extension_infobar_controller.mm b/chrome/browser/cocoa/extensions/extension_infobar_controller.mm
index 1bb1a5f..a2a38f2 100644
--- a/chrome/browser/cocoa/extensions/extension_infobar_controller.mm
+++ b/chrome/browser/cocoa/extensions/extension_infobar_controller.mm
@@ -65,7 +65,7 @@ class InfobarBridge : public ExtensionInfoBarDelegate::DelegateObserver,
 
   // Load the Extension's icon image.
   void LoadIcon() {
-    Extension* extension = delegate_->extension_host()->extension();
+    const Extension* extension = delegate_->extension_host()->extension();
     ExtensionResource icon_resource = extension->GetIconResource(
         Extension::EXTENSION_ICON_BITTY, ExtensionIconSet::MATCH_EXACTLY);
     if (!icon_resource.relative_path().empty()) {
diff --git a/chrome/browser/cocoa/extensions/extension_install_prompt_controller.h b/chrome/browser/cocoa/extensions/extension_install_prompt_controller.h
index 0fb4d4e..8a6a4ce 100644
--- a/chrome/browser/cocoa/extensions/extension_install_prompt_controller.h
+++ b/chrome/browser/cocoa/extensions/extension_install_prompt_controller.h
@@ -49,7 +49,7 @@ class Profile;
 
 - (id)initWithParentWindow:(NSWindow*)window
                    profile:(Profile*)profile
-                 extension:(Extension*)extension
+                 extension:(const Extension*)extension
                   delegate:(ExtensionInstallUI::Delegate*)delegate
                       icon:(SkBitmap*)bitmap
                   warnings:(const std::vector<string16>&)warnings;
diff --git a/chrome/browser/cocoa/extensions/extension_install_prompt_controller.mm b/chrome/browser/cocoa/extensions/extension_install_prompt_controller.mm
index 9ba758b..10f4f81 100644
--- a/chrome/browser/cocoa/extensions/extension_install_prompt_controller.mm
+++ b/chrome/browser/cocoa/extensions/extension_install_prompt_controller.mm
@@ -58,7 +58,7 @@ void OffsetControlVertically(NSControl* control, CGFloat amount) {
 
 - (id)initWithParentWindow:(NSWindow*)window
                    profile:(Profile*)profile
-                 extension:(Extension*)extension
+                 extension:(const Extension*)extension
                   delegate:(ExtensionInstallUI::Delegate*)delegate
                       icon:(SkBitmap*)icon
                   warnings:(const std::vector<string16>&)warnings {
@@ -185,7 +185,10 @@ void OffsetControlVertically(NSControl* control, CGFloat amount) {
 
 
 void ExtensionInstallUI::ShowExtensionInstallUIPrompt2Impl(
-    Profile* profile, Delegate* delegate, Extension* extension, SkBitmap* icon,
+    Profile* profile,
+    Delegate* delegate,
+    const Extension* extension,
+    SkBitmap* icon,
     const std::vector<string16>& warnings) {
   Browser* browser = BrowserList::GetLastActiveWithProfile(profile);
   if (!browser) {
diff --git a/chrome/browser/cocoa/location_bar/page_action_decoration.mm b/chrome/browser/cocoa/location_bar/page_action_decoration.mm
index 572a65a..79636b2 100644
--- a/chrome/browser/cocoa/location_bar/page_action_decoration.mm
+++ b/chrome/browser/cocoa/location_bar/page_action_decoration.mm
@@ -39,8 +39,8 @@ PageActionDecoration::PageActionDecoration(
       current_tab_id_(-1),
       preview_enabled_(false) {
   DCHECK(profile);
-  Extension* extension = profile->GetExtensionsService()->GetExtensionById(
-      page_action->extension_id(), false);
+  const Extension* extension = profile->GetExtensionsService()->
+      GetExtensionById(page_action->extension_id(), false);
   DCHECK(extension);
 
   // Load all the icons declared in the manifest. This is the contents of the
@@ -219,7 +219,7 @@ NSMenu* PageActionDecoration::GetMenu() {
   ExtensionsService* service = profile_->GetExtensionsService();
   if (!service)
     return nil;
-  Extension* extension = service->GetExtensionById(
+  const Extension* extension = service->GetExtensionById(
       page_action_->extension_id(), false);
   DCHECK(extension);
   if (!extension)
diff --git a/chrome/browser/dom_ui/app_launcher_handler.cc b/chrome/browser/dom_ui/app_launcher_handler.cc
index f3309c92..9bc27d2 100644
--- a/chrome/browser/dom_ui/app_launcher_handler.cc
+++ b/chrome/browser/dom_ui/app_launcher_handler.cc
@@ -44,7 +44,7 @@ bool ExtractInt(const ListValue* list, size_t index, int* out_int) {
   return false;
 }
 
-std::string GetIconURL(Extension* extension, Extension::Icons icon,
+std::string GetIconURL(const Extension* extension, Extension::Icons icon,
                        const std::string& default_val) {
   GURL url = extension->GetIconURL(icon, ExtensionIconSet::MATCH_EXACTLY);
   if (!url.is_empty())
@@ -103,7 +103,7 @@ void AppLauncherHandler::Observe(NotificationType type,
 }
 
 // static
-void AppLauncherHandler::CreateAppInfo(Extension* extension,
+void AppLauncherHandler::CreateAppInfo(const Extension* extension,
                                        ExtensionPrefs* extension_prefs,
                                        DictionaryValue* value) {
   value->Clear();
@@ -202,7 +202,7 @@ void AppLauncherHandler::HandleLaunchApp(const ListValue* args) {
   dom_ui_->tab_contents()->GetContainerBounds(&tab_contents_bounds);
   rect.Offset(tab_contents_bounds.origin());
 
-  Extension* extension =
+  const Extension* extension =
       extensions_service_->GetExtensionById(extension_id, false);
   DCHECK(extension);
   Profile* profile = extensions_service_->profile();
@@ -231,7 +231,7 @@ void AppLauncherHandler::HandleSetLaunchType(const ListValue* args) {
     return;
   }
 
-  Extension* extension =
+  const Extension* extension =
       extensions_service_->GetExtensionById(extension_id, false);
   DCHECK(extension);
 
@@ -240,7 +240,7 @@ void AppLauncherHandler::HandleSetLaunchType(const ListValue* args) {
       static_cast<ExtensionPrefs::LaunchType>(launch_type));
 }
 
-void AppLauncherHandler::AnimateAppIcon(Extension* extension,
+void AppLauncherHandler::AnimateAppIcon(const Extension* extension,
                                         const gfx::Rect& rect) {
   // We make this check for the case of minimized windows, unit tests, etc.
   if (platform_util::IsVisible(dom_ui_->tab_contents()->GetNativeView()) &&
@@ -255,7 +255,7 @@ void AppLauncherHandler::AnimateAppIcon(Extension* extension,
 
 void AppLauncherHandler::HandleUninstallApp(const ListValue* args) {
   std::string extension_id = WideToUTF8(ExtractStringValue(args));
-  Extension* extension = extensions_service_->GetExtensionById(
+  const Extension* extension = extensions_service_->GetExtensionById(
       extension_id, false);
   if (!extension)
     return;
@@ -295,7 +295,7 @@ void AppLauncherHandler::InstallUIProceed() {
 
   // The extension can be uninstalled in another window while the UI was
   // showing. Do nothing in that case.
-  Extension* extension =
+  const Extension* extension =
       extensions_service_->GetExtensionById(extension_id_prompting_, true);
   if (!extension)
     return;
diff --git a/chrome/browser/dom_ui/app_launcher_handler.h b/chrome/browser/dom_ui/app_launcher_handler.h
index c3ca622..5a3478e 100644
--- a/chrome/browser/dom_ui/app_launcher_handler.h
+++ b/chrome/browser/dom_ui/app_launcher_handler.h
@@ -42,7 +42,7 @@ class AppLauncherHandler
                       const NotificationDetails& details);
 
   // Populate a dictionary with the information from an extension.
-  static void CreateAppInfo(Extension* extension,
+  static void CreateAppInfo(const Extension* extension,
                             ExtensionPrefs* extension_prefs,
                             DictionaryValue* value);
 
@@ -75,7 +75,7 @@ class AppLauncherHandler
   ExtensionInstallUI* GetExtensionInstallUI();
 
   // Starts the animation of the app icon.
-  void AnimateAppIcon(Extension* extension, const gfx::Rect& rect);
+  void AnimateAppIcon(const Extension* extension, const gfx::Rect& rect);
 
   // The apps are represented in the extensions model.
   scoped_refptr<ExtensionsService> extensions_service_;
diff --git a/chrome/browser/extensions/alert_apitest.cc b/chrome/browser/extensions/alert_apitest.cc
index 23e8fe8..8e70fdb 100644
--- a/chrome/browser/extensions/alert_apitest.cc
+++ b/chrome/browser/extensions/alert_apitest.cc
@@ -14,7 +14,7 @@
 IN_PROC_BROWSER_TEST_F(ExtensionApiTest, AlertBasic) {
   ASSERT_TRUE(RunExtensionTest("alert")) << message_;
 
-  Extension* extension = GetSingleLoadedExtension();
+  const Extension* extension = GetSingleLoadedExtension();
   ExtensionHost* host = browser()->profile()->GetExtensionProcessManager()->
       GetBackgroundHostForExtension(extension);
   ASSERT_TRUE(host);
diff --git a/chrome/browser/extensions/browser_action_apitest.cc b/chrome/browser/extensions/browser_action_apitest.cc
index 8b09783..5e76310 100644
--- a/chrome/browser/extensions/browser_action_apitest.cc
+++ b/chrome/browser/extensions/browser_action_apitest.cc
@@ -47,7 +47,7 @@ class BrowserActionApiTest : public ExtensionApiTest {
 IN_PROC_BROWSER_TEST_F(BrowserActionApiTest, Basic) {
   ASSERT_TRUE(test_server()->Start());
   ASSERT_TRUE(RunExtensionTest("browser_action/basics")) << message_;
-  Extension* extension = GetSingleLoadedExtension();
+  const Extension* extension = GetSingleLoadedExtension();
   ASSERT_TRUE(extension) << message_;
 
   // Test that there is a browser action in the toolbar.
@@ -87,7 +87,7 @@ IN_PROC_BROWSER_TEST_F(BrowserActionApiTest, Basic) {
 
 IN_PROC_BROWSER_TEST_F(BrowserActionApiTest, DynamicBrowserAction) {
   ASSERT_TRUE(RunExtensionTest("browser_action/no_icon")) << message_;
-  Extension* extension = GetSingleLoadedExtension();
+  const Extension* extension = GetSingleLoadedExtension();
   ASSERT_TRUE(extension) << message_;
 
   // Test that there is a browser action in the toolbar and that it has no icon.
@@ -117,7 +117,7 @@ IN_PROC_BROWSER_TEST_F(BrowserActionApiTest, DynamicBrowserAction) {
 IN_PROC_BROWSER_TEST_F(BrowserActionApiTest, TabSpecificBrowserActionState) {
   ASSERT_TRUE(RunExtensionTest("browser_action/tab_specific_state")) <<
       message_;
-  Extension* extension = GetSingleLoadedExtension();
+  const Extension* extension = GetSingleLoadedExtension();
   ASSERT_TRUE(extension) << message_;
 
   // Test that there is a browser action in the toolbar and that it has an icon.
@@ -147,7 +147,7 @@ IN_PROC_BROWSER_TEST_F(BrowserActionApiTest, BrowserActionPopup) {
   ASSERT_TRUE(LoadExtension(test_data_dir_.AppendASCII(
       "browser_action/popup")));
   BrowserActionTestUtil actions_bar = GetBrowserActionsBar();
-  Extension* extension = GetSingleLoadedExtension();
+  const Extension* extension = GetSingleLoadedExtension();
   ASSERT_TRUE(extension) << message_;
 
   // The extension's popup's size grows by |growFactor| each click.
@@ -180,7 +180,7 @@ IN_PROC_BROWSER_TEST_F(BrowserActionApiTest, BrowserActionPopup) {
 // a popup.
 IN_PROC_BROWSER_TEST_F(BrowserActionApiTest, BrowserActionAddPopup) {
   ASSERT_TRUE(RunExtensionTest("browser_action/add_popup")) << message_;
-  Extension* extension = GetSingleLoadedExtension();
+  const Extension* extension = GetSingleLoadedExtension();
   ASSERT_TRUE(extension) << message_;
 
   int tab_id = ExtensionTabUtil::GetTabId(browser()->GetSelectedTabContents());
@@ -235,7 +235,7 @@ IN_PROC_BROWSER_TEST_F(BrowserActionApiTest, BrowserActionAddPopup) {
 IN_PROC_BROWSER_TEST_F(BrowserActionApiTest, BrowserActionRemovePopup) {
   // Load the extension, which has a browser action with a default popup.
   ASSERT_TRUE(RunExtensionTest("browser_action/remove_popup")) << message_;
-  Extension* extension = GetSingleLoadedExtension();
+  const Extension* extension = GetSingleLoadedExtension();
   ASSERT_TRUE(extension) << message_;
 
   int tab_id = ExtensionTabUtil::GetTabId(browser()->GetSelectedTabContents());
@@ -269,7 +269,7 @@ IN_PROC_BROWSER_TEST_F(BrowserActionApiTest, IncognitoBasic) {
   ASSERT_TRUE(test_server()->Start());
 
   ASSERT_TRUE(RunExtensionTest("browser_action/basics")) << message_;
-  Extension* extension = GetSingleLoadedExtension();
+  const Extension* extension = GetSingleLoadedExtension();
   ASSERT_TRUE(extension) << message_;
 
   // Test that there is a browser action in the toolbar.
diff --git a/chrome/browser/extensions/crx_installer.cc b/chrome/browser/extensions/crx_installer.cc
index 07aa3d08..17276f7 100644
--- a/chrome/browser/extensions/crx_installer.cc
+++ b/chrome/browser/extensions/crx_installer.cc
@@ -157,7 +157,8 @@ void CrxInstaller::ConvertUserScriptOnFileThread() {
   OnUnpackSuccess(extension->path(), extension->path(), extension);
 }
 
-bool CrxInstaller::AllowInstall(Extension* extension, std::string* error) {
+bool CrxInstaller::AllowInstall(const Extension* extension,
+                                std::string* error) {
   DCHECK(error);
 
   // We always allow themes and external installs.
@@ -239,7 +240,7 @@ void CrxInstaller::OnUnpackFailure(const std::string& error_message) {
 
 void CrxInstaller::OnUnpackSuccess(const FilePath& temp_dir,
                                    const FilePath& extension_dir,
-                                   Extension* extension) {
+                                   const Extension* extension) {
   DCHECK(BrowserThread::CurrentlyOn(BrowserThread::FILE));
 
   // Note: We take ownership of |extension| and |temp_dir|.
@@ -282,7 +283,7 @@ void CrxInstaller::ConfirmInstall() {
   }
 
   GURL overlapping_url;
-  Extension* overlapping_extension =
+  const Extension* overlapping_extension =
       frontend_->GetExtensionByOverlappingWebExtent(extension_->web_extent());
   if (overlapping_extension) {
     ReportFailureFromUIThread(l10n_util::GetStringFUTF8(
diff --git a/chrome/browser/extensions/crx_installer.h b/chrome/browser/extensions/crx_installer.h
index 8263095..73d5af8 100644
--- a/chrome/browser/extensions/crx_installer.h
+++ b/chrome/browser/extensions/crx_installer.h
@@ -120,13 +120,13 @@ class CrxInstaller
 
   // Called after OnUnpackSuccess as a last check to see whether the install
   // should complete.
-  bool AllowInstall(Extension* extension, std::string* error);
+  bool AllowInstall(const Extension* extension, std::string* error);
 
   // SandboxedExtensionUnpackerClient
   virtual void OnUnpackFailure(const std::string& error_message);
   virtual void OnUnpackSuccess(const FilePath& temp_dir,
                                const FilePath& extension_dir,
-                               Extension* extension);
+                               const Extension* extension);
 
   // Runs on the UI thread. Confirms with the user (via ExtensionInstallUI) that
   // it is OK to install this extension.
@@ -187,7 +187,7 @@ class CrxInstaller
 
   // The extension we're installing. We own this and either pass it off to
   // ExtensionsService on success, or delete it on failure.
-  scoped_refptr<Extension> extension_;
+  scoped_refptr<const Extension> extension_;
 
   // If non-empty, contains the current version of the extension we're
   // installing (for upgrades).
diff --git a/chrome/browser/extensions/execute_code_in_tab_function.cc b/chrome/browser/extensions/execute_code_in_tab_function.cc
index b7bf999..8021e6c 100644
--- a/chrome/browser/extensions/execute_code_in_tab_function.cc
+++ b/chrome/browser/extensions/execute_code_in_tab_function.cc
@@ -78,7 +78,7 @@ bool ExecuteCodeInTabFunction::RunImpl() {
 
   // NOTE: This can give the wrong answer due to race conditions, but it is OK,
   // we check again in the renderer.
-  Extension* extension = GetExtension();
+  const Extension* extension = GetExtension();
   const std::vector<URLPattern> host_permissions =
       extension->host_permissions();
   if (!Extension::CanExecuteScriptOnPage(
@@ -158,7 +158,7 @@ bool ExecuteCodeInTabFunction::Execute(const std::string& code_string) {
     return false;
   }
 
-  Extension* extension = GetExtension();
+  const Extension* extension = GetExtension();
   if (!extension) {
     SendResponse(false);
     return false;
diff --git a/chrome/browser/extensions/extension_apitest.cc b/chrome/browser/extensions/extension_apitest.cc
index 0547554..07668b3 100644
--- a/chrome/browser/extensions/extension_apitest.cc
+++ b/chrome/browser/extensions/extension_apitest.cc
@@ -144,7 +144,7 @@ bool ExtensionApiTest::RunExtensionTestImpl(const char* extension_name,
           "Relative page_url given with no extension_name";
 
       ExtensionsService* service = browser()->profile()->GetExtensionsService();
-      Extension* extension =
+      const Extension* extension =
           service->GetExtensionById(last_loaded_extension_id_, false);
       if (!extension)
         return false;
@@ -165,7 +165,7 @@ bool ExtensionApiTest::RunExtensionTestImpl(const char* extension_name,
 }
 
 // Test that exactly one extension loaded.
-Extension* ExtensionApiTest::GetSingleLoadedExtension() {
+const Extension* ExtensionApiTest::GetSingleLoadedExtension() {
   ExtensionsService* service = browser()->profile()->GetExtensionsService();
 
   int found_extension_index = -1;
@@ -185,7 +185,7 @@ Extension* ExtensionApiTest::GetSingleLoadedExtension() {
     found_extension_index = static_cast<int>(i);
   }
 
-  Extension* extension = service->extensions()->at(found_extension_index);
+  const Extension* extension = service->extensions()->at(found_extension_index);
   if (!extension) {
     message_ = "extension pointer is NULL.";
     return NULL;
diff --git a/chrome/browser/extensions/extension_apitest.h b/chrome/browser/extensions/extension_apitest.h
index b0a0e01..b2079a6 100644
--- a/chrome/browser/extensions/extension_apitest.h
+++ b/chrome/browser/extensions/extension_apitest.h
@@ -94,7 +94,7 @@ 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_.
-  Extension* GetSingleLoadedExtension();
+  const Extension* GetSingleLoadedExtension();
 
   // All extensions tested by ExtensionApiTest are in the "api_test" dir.
   virtual void SetUpCommandLine(CommandLine* command_line);
diff --git a/chrome/browser/extensions/extension_browser_actions_api.cc b/chrome/browser/extensions/extension_browser_actions_api.cc
index 1ce4dfe..1986d28 100644
--- a/chrome/browser/extensions/extension_browser_actions_api.cc
+++ b/chrome/browser/extensions/extension_browser_actions_api.cc
@@ -26,7 +26,7 @@ bool BrowserActionFunction::RunImpl() {
   if (details_->HasKey("tabId"))
     EXTENSION_FUNCTION_VALIDATE(details_->GetInteger("tabId", &tab_id_));
 
-  Extension* extension = GetExtension();
+  const Extension* extension = GetExtension();
   browser_action_ = extension->browser_action();
   if (!browser_action_) {
     error_ = kNoBrowserActionError;
diff --git a/chrome/browser/extensions/extension_browsertest.cc b/chrome/browser/extensions/extension_browsertest.cc
index 7c4cd83..af8a6de 100644
--- a/chrome/browser/extensions/extension_browsertest.cc
+++ b/chrome/browser/extensions/extension_browsertest.cc
@@ -69,7 +69,7 @@ bool ExtensionBrowserTest::LoadExtensionImpl(const FilePath& path,
   // Find the extension by iterating backwards since it is likely last.
   FilePath extension_path = path;
   file_util::AbsolutePath(&extension_path);
-  Extension* extension = NULL;
+  const Extension* extension = NULL;
   for (ExtensionList::const_reverse_iterator iter =
            service->extensions()->rbegin();
        iter != service->extensions()->rend(); ++iter) {
@@ -107,14 +107,15 @@ class MockAbortExtensionInstallUI : public ExtensionInstallUI {
   MockAbortExtensionInstallUI() : ExtensionInstallUI(NULL) {}
 
   // Simulate a user abort on an extension installation.
-  virtual void ConfirmInstall(Delegate* delegate, Extension* extension) {
+  virtual void ConfirmInstall(Delegate* delegate, const Extension* extension) {
     delegate->InstallUIAbort();
     MessageLoopForUI::current()->Quit();
   }
 
-  virtual void ConfirmUninstall(Delegate* delegate, Extension* extension) {}
+  virtual void ConfirmUninstall(Delegate* delegate,
+                                const Extension* extension) {}
 
-  virtual void OnInstallSuccess(Extension* extension) {}
+  virtual void OnInstallSuccess(const Extension* extension) {}
 
   virtual void OnInstallFailure(const std::string& error) {}
 };
@@ -288,7 +289,7 @@ void ExtensionBrowserTest::Observe(NotificationType type,
                                    const NotificationDetails& details) {
   switch (type.value) {
     case NotificationType::EXTENSION_LOADED:
-      last_loaded_extension_id_ = Details<Extension>(details).ptr()->id();
+      last_loaded_extension_id_ = Details<const Extension>(details).ptr()->id();
       VLOG(1) << "Got EXTENSION_LOADED notification.";
       MessageLoopForUI::current()->Quit();
       break;
diff --git a/chrome/browser/extensions/extension_browsertests_misc.cc b/chrome/browser/extensions/extension_browsertests_misc.cc
index 903e0ff..3b1780d 100644
--- a/chrome/browser/extensions/extension_browsertests_misc.cc
+++ b/chrome/browser/extensions/extension_browsertests_misc.cc
@@ -260,13 +260,13 @@ IN_PROC_BROWSER_TEST_F(ExtensionBrowserTest, PageActionRefreshCrash) {
   ASSERT_TRUE(LoadExtension(base_path.AppendASCII("ExtA")));
   ASSERT_TRUE(WaitForPageActionVisibilityChangeTo(1));
   ASSERT_EQ(size_before + 1, service->extensions()->size());
-  Extension* extensionA = service->extensions()->at(size_before);
+  const Extension* extensionA = service->extensions()->at(size_before);
 
   // Load extension B.
   ASSERT_TRUE(LoadExtension(base_path.AppendASCII("ExtB")));
   ASSERT_TRUE(WaitForPageActionVisibilityChangeTo(2));
   ASSERT_EQ(size_before + 2, service->extensions()->size());
-  Extension* extensionB = service->extensions()->at(size_before + 1);
+  const Extension* extensionB = service->extensions()->at(size_before + 1);
 
   ReloadExtension(extensionA->id());
   // ExtensionA has changed, so refetch it.
@@ -306,7 +306,7 @@ IN_PROC_BROWSER_TEST_F(ExtensionBrowserTest, TitleLocalizationBrowserAction) {
   ASSERT_TRUE(LoadExtension(extension_path));
 
   ASSERT_EQ(size_before + 1, service->extensions()->size());
-  Extension* extension = service->extensions()->at(size_before);
+  const Extension* extension = service->extensions()->at(size_before);
 
   EXPECT_STREQ(WideToUTF8(L"Hreggvi\u00F0ur: l10n browser action").c_str(),
                extension->description().c_str());
@@ -335,7 +335,7 @@ IN_PROC_BROWSER_TEST_F(ExtensionBrowserTest, TitleLocalizationPageAction) {
   ASSERT_TRUE(WaitForPageActionVisibilityChangeTo(1));
 
   ASSERT_EQ(size_before + 1, service->extensions()->size());
-  Extension* extension = service->extensions()->at(size_before);
+  const Extension* extension = service->extensions()->at(size_before);
 
   EXPECT_STREQ(WideToUTF8(L"Hreggvi\u00F0ur: l10n page action").c_str(),
                extension->description().c_str());
@@ -422,7 +422,7 @@ void NavigateToFeedAndValidate(net::TestServer* server,
   }
 
   ExtensionsService* service = browser->profile()->GetExtensionsService();
-  Extension* extension = service->extensions()->back();
+  const Extension* extension = service->extensions()->back();
   std::string id = extension->id();
 
   // Navigate to the subscribe page directly.
@@ -778,7 +778,7 @@ IN_PROC_BROWSER_TEST_F(ExtensionBrowserTest, DISABLED_OptionsPage) {
   ExtensionsService* service = browser()->profile()->GetExtensionsService();
   const ExtensionList* extensions = service->extensions();
   ASSERT_EQ(1u, extensions->size());
-  Extension* extension = extensions->at(0);
+  const Extension* extension = extensions->at(0);
 
   // Go to the chrome://extensions page and click the Options button.
   ui_test_utils::NavigateToURL(browser(), GURL(chrome::kChromeUIExtensionsURL));
diff --git a/chrome/browser/extensions/extension_context_menu_browsertest.cc b/chrome/browser/extensions/extension_context_menu_browsertest.cc
index 62221e1..b0041ad 100644
--- a/chrome/browser/extensions/extension_context_menu_browsertest.cc
+++ b/chrome/browser/extensions/extension_context_menu_browsertest.cc
@@ -142,7 +142,7 @@ class ExtensionContextMenuBrowserTest : public ExtensionBrowserTest {
 
   // Returns a pointer to the currently loaded extension with |name|, or null
   // if not found.
-  Extension* GetExtensionNamed(std::string name) {
+  const Extension* GetExtensionNamed(std::string name) {
     const ExtensionList* extensions =
         browser()->profile()->GetExtensionsService()->extensions();
     ExtensionList::const_iterator i;
@@ -301,7 +301,7 @@ static void VerifyMenuForSeparatorsTest(const MenuModel& menu) {
 IN_PROC_BROWSER_TEST_F(ExtensionContextMenuBrowserTest, Separators) {
   // Load the extension.
   ASSERT_TRUE(LoadContextMenuExtension("separators"));
-  Extension* extension = GetExtensionNamed("Separators Test");
+  const 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 6432f9d..404241e 100644
--- a/chrome/browser/extensions/extension_context_menu_model.cc
+++ b/chrome/browser/extensions/extension_context_menu_model.cc
@@ -28,7 +28,7 @@ enum MenuEntries {
 };
 
 ExtensionContextMenuModel::ExtensionContextMenuModel(
-    Extension* extension,
+    const Extension* extension,
     Browser* browser,
     PopupDelegate* delegate)
     : ALLOW_THIS_IN_INITIALIZER_LIST(SimpleMenuModel(this)),
@@ -53,7 +53,7 @@ ExtensionContextMenuModel::~ExtensionContextMenuModel() {
 }
 
 void ExtensionContextMenuModel::InitCommonCommands() {
-  Extension* extension = GetExtension();
+  const Extension* extension = GetExtension();
 
   // The extension pointer should only be null if the extension was uninstalled,
   // and since the menu just opened, it should still be installed.
@@ -73,7 +73,7 @@ bool ExtensionContextMenuModel::IsCommandIdChecked(int command_id) const {
 }
 
 bool ExtensionContextMenuModel::IsCommandIdEnabled(int command_id) const {
-  Extension* extension = this->GetExtension();
+  const Extension* extension = this->GetExtension();
   if (!extension)
     return false;
 
@@ -99,7 +99,7 @@ bool ExtensionContextMenuModel::GetAcceleratorForCommandId(
 }
 
 void ExtensionContextMenuModel::ExecuteCommand(int command_id) {
-  Extension* extension = GetExtension();
+  const Extension* extension = GetExtension();
   if (!extension)
     return;
 
@@ -151,7 +151,7 @@ void ExtensionContextMenuModel::InstallUIAbort() {
   Release();
 }
 
-Extension* ExtensionContextMenuModel::GetExtension() const {
+const Extension* ExtensionContextMenuModel::GetExtension() const {
   ExtensionsService* extension_service = profile_->GetExtensionsService();
   return extension_service->GetExtensionById(extension_id_, false);
 }
diff --git a/chrome/browser/extensions/extension_context_menu_model.h b/chrome/browser/extensions/extension_context_menu_model.h
index e7c5b31..89cf3f9 100644
--- a/chrome/browser/extensions/extension_context_menu_model.h
+++ b/chrome/browser/extensions/extension_context_menu_model.h
@@ -37,7 +37,7 @@ class ExtensionContextMenuModel
   // prefs::kExtensionsUIDeveloperMode is enabled then a menu item
   // will be shown for "Inspect Popup" which, when selected, will cause
   // ShowPopupForDevToolsWindow() to be called on |delegate|.
-  ExtensionContextMenuModel(Extension* extension,
+  ExtensionContextMenuModel(const Extension* extension,
                             Browser* browser,
                             PopupDelegate* delegate);
   virtual ~ExtensionContextMenuModel();
@@ -58,7 +58,7 @@ class ExtensionContextMenuModel
 
   // Gets the extension we are displaying the menu for. Returns NULL if the
   // extension has been uninstalled and no longer exists.
-  Extension* GetExtension() const;
+  const 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 32b67af..3ad8813 100644
--- a/chrome/browser/extensions/extension_crash_recovery_browsertest.cc
+++ b/chrome/browser/extensions/extension_crash_recovery_browsertest.cc
@@ -51,7 +51,8 @@ class ExtensionCrashRecoveryTest : public ExtensionBrowserTest {
 
   void CrashExtension(size_t index) {
     ASSERT_LT(index, GetExtensionsService()->extensions()->size());
-    Extension* extension = GetExtensionsService()->extensions()->at(index);
+    const Extension* extension =
+        GetExtensionsService()->extensions()->at(index);
     ASSERT_TRUE(extension);
     std::string extension_id(extension->id());
     ExtensionHost* extension_host =
@@ -69,7 +70,8 @@ class ExtensionCrashRecoveryTest : public ExtensionBrowserTest {
 
   void CheckExtensionConsistency(size_t index) {
     ASSERT_LT(index, GetExtensionsService()->extensions()->size());
-    Extension* extension = GetExtensionsService()->extensions()->at(index);
+    const Extension* extension =
+        GetExtensionsService()->extensions()->at(index);
     ASSERT_TRUE(extension);
     ExtensionHost* extension_host =
         GetExtensionProcessManager()->GetBackgroundHostForExtension(extension);
@@ -85,7 +87,7 @@ class ExtensionCrashRecoveryTest : public ExtensionBrowserTest {
     const size_t size_before = GetExtensionsService()->extensions()->size();
     ASSERT_TRUE(LoadExtension(
         test_data_dir_.AppendASCII("common").AppendASCII("background_page")));
-    Extension* extension = GetExtensionsService()->extensions()->back();
+    const Extension* extension = GetExtensionsService()->extensions()->back();
     ASSERT_TRUE(extension);
     first_extension_id_ = extension->id();
     CheckExtensionConsistency(size_before);
@@ -95,7 +97,8 @@ class ExtensionCrashRecoveryTest : public ExtensionBrowserTest {
     int offset = GetExtensionsService()->extensions()->size();
     ASSERT_TRUE(LoadExtension(
         test_data_dir_.AppendASCII("install").AppendASCII("install")));
-    Extension* extension = GetExtensionsService()->extensions()->at(offset);
+    const Extension* extension =
+        GetExtensionsService()->extensions()->at(offset);
     ASSERT_TRUE(extension);
     second_extension_id_ = extension->id();
     CheckExtensionConsistency(offset);
diff --git a/chrome/browser/extensions/extension_disabled_infobar_delegate.cc b/chrome/browser/extensions/extension_disabled_infobar_delegate.cc
index 6e51c47..af38e4f 100644
--- a/chrome/browser/extensions/extension_disabled_infobar_delegate.cc
+++ b/chrome/browser/extensions/extension_disabled_infobar_delegate.cc
@@ -26,7 +26,7 @@ class ExtensionDisabledDialogDelegate
  public:
   ExtensionDisabledDialogDelegate(Profile* profile,
                                   ExtensionsService* service,
-                                  Extension* extension)
+                                  const Extension* extension)
         : service_(service), extension_(extension) {
     AddRef();  // Balanced in Proceed or Abort.
 
@@ -55,7 +55,7 @@ class ExtensionDisabledDialogDelegate
   scoped_ptr<ExtensionInstallUI> install_ui_;
 
   ExtensionsService* service_;
-  Extension* extension_;
+  const Extension* extension_;
 };
 
 class ExtensionDisabledInfobarDelegate
@@ -64,7 +64,7 @@ class ExtensionDisabledInfobarDelegate
  public:
   ExtensionDisabledInfobarDelegate(TabContents* tab_contents,
                                    ExtensionsService* service,
-                                   Extension* extension)
+                                   const Extension* extension)
       : ConfirmInfoBarDelegate(tab_contents),
         tab_contents_(tab_contents),
         service_(service),
@@ -110,7 +110,7 @@ class ExtensionDisabledInfobarDelegate
     switch (type.value) {
       case NotificationType::EXTENSION_LOADED:
       case NotificationType::EXTENSION_UNLOADED_DISABLED: {
-        Extension* extension = Details<Extension>(details).ptr();
+        const Extension* extension = Details<const Extension>(details).ptr();
         if (extension == extension_)
           tab_contents_->RemoveInfoBar(this);
         break;
@@ -124,11 +124,11 @@ class ExtensionDisabledInfobarDelegate
   NotificationRegistrar registrar_;
   TabContents* tab_contents_;
   ExtensionsService* service_;
-  Extension* extension_;
+  const Extension* extension_;
 };
 
 void ShowExtensionDisabledUI(ExtensionsService* service, Profile* profile,
-                             Extension* extension) {
+                             const Extension* extension) {
   Browser* browser = BrowserList::GetLastActiveWithProfile(profile);
   if (!browser)
     return;
@@ -142,7 +142,7 @@ void ShowExtensionDisabledUI(ExtensionsService* service, Profile* profile,
 }
 
 void ShowExtensionDisabledDialog(ExtensionsService* service, Profile* profile,
-                                 Extension* extension) {
+                                 const Extension* extension) {
   // This object manages its own lifetime.
   new ExtensionDisabledDialogDelegate(profile, service, extension);
 }
diff --git a/chrome/browser/extensions/extension_disabled_infobar_delegate.h b/chrome/browser/extensions/extension_disabled_infobar_delegate.h
index 16d3b6f..430e652 100644
--- a/chrome/browser/extensions/extension_disabled_infobar_delegate.h
+++ b/chrome/browser/extensions/extension_disabled_infobar_delegate.h
@@ -13,10 +13,10 @@ class Profile;
 // Shows UI to inform the user that an extension was disabled after upgrading
 // to higher permissions.
 void ShowExtensionDisabledUI(ExtensionsService* service, Profile* profile,
-                             Extension* extension);
+                             const Extension* extension);
 
 // Shows the extension install dialog.
 void ShowExtensionDisabledDialog(ExtensionsService* service, Profile* profile,
-                                 Extension* extension);
+                                 const Extension* extension);
 
 #endif  // CHROME_BROWSER_EXTENSIONS_EXTENSION_DISABLED_INFOBAR_DELEGATE_H_
diff --git a/chrome/browser/extensions/extension_dom_ui.cc b/chrome/browser/extensions/extension_dom_ui.cc
index 29c5aab..054eb1e 100644
--- a/chrome/browser/extensions/extension_dom_ui.cc
+++ b/chrome/browser/extensions/extension_dom_ui.cc
@@ -112,7 +112,7 @@ class ExtensionDOMUIImageLoadingTracker : public ImageLoadingTracker::Observer {
 
   ImageLoadingTracker tracker_;
   scoped_refptr<FaviconService::GetFaviconRequest> request_;
-  Extension* extension_;
+  const Extension* extension_;
 
   DISALLOW_COPY_AND_ASSIGN(ExtensionDOMUIImageLoadingTracker);
 };
@@ -126,7 +126,7 @@ ExtensionDOMUI::ExtensionDOMUI(TabContents* tab_contents, GURL url)
     : DOMUI(tab_contents),
       url_(url) {
   ExtensionsService* service = tab_contents->profile()->GetExtensionsService();
-  Extension* extension = service->GetExtensionByURL(url);
+  const Extension* extension = service->GetExtensionByURL(url);
   if (!extension)
     extension = service->GetExtensionByWebExtent(url);
   DCHECK(extension);
@@ -271,7 +271,7 @@ bool ExtensionDOMUI::HandleChromeURLOverride(GURL* url, Profile* profile) {
     }
 
     // Verify that the extension that's being referred to actually exists.
-    Extension* extension = service->GetExtensionByURL(extension_url);
+    const Extension* extension = service->GetExtensionByURL(extension_url);
     if (!extension) {
       // This can currently happen if you use --load-extension one run, and
       // then don't use it the next.  It could also happen if an extension
diff --git a/chrome/browser/extensions/extension_event_router.cc b/chrome/browser/extensions/extension_event_router.cc
index 9d22da7..b1577167 100644
--- a/chrome/browser/extensions/extension_event_router.cc
+++ b/chrome/browser/extensions/extension_event_router.cc
@@ -38,7 +38,7 @@ static bool CanCrossIncognito(Profile* profile,
   // We allow the extension to see events and data from another profile iff it
   // uses "spanning" behavior and it has incognito access. "split" mode
   // extensions only see events for a matching profile.
-  Extension* extension =
+  const Extension* extension =
       profile->GetExtensionsService()->GetExtensionById(extension_id, false);
   return (profile->GetExtensionsService()->IsIncognitoEnabled(extension) &&
           !extension->incognito_split_mode());
diff --git a/chrome/browser/extensions/extension_function.cc b/chrome/browser/extensions/extension_function.cc
index f285e9d..88a6c9e 100644
--- a/chrome/browser/extensions/extension_function.cc
+++ b/chrome/browser/extensions/extension_function.cc
@@ -21,7 +21,7 @@ ExtensionFunction::ExtensionFunction()
 ExtensionFunction::~ExtensionFunction() {
 }
 
-Extension* ExtensionFunction::GetExtension() {
+const Extension* ExtensionFunction::GetExtension() {
   ExtensionsService* service = profile_->GetExtensionsService();
   DCHECK(service);
   return service->GetExtensionById(extension_id_, false);
diff --git a/chrome/browser/extensions/extension_function.h b/chrome/browser/extensions/extension_function.h
index b48d0a9..57a8665 100644
--- a/chrome/browser/extensions/extension_function.h
+++ b/chrome/browser/extensions/extension_function.h
@@ -107,7 +107,7 @@ class ExtensionFunction : public base::RefCountedThreadSafe<ExtensionFunction> {
   // Gets the extension that called this function. This can return NULL for
   // async functions, for example if the extension is unloaded while the
   // function is running.
-  Extension* GetExtension();
+  const Extension* GetExtension();
 
   // Gets the "current" browser, if any.
   //
diff --git a/chrome/browser/extensions/extension_function_dispatcher.cc b/chrome/browser/extensions/extension_function_dispatcher.cc
index e3ca590..783a8bf 100644
--- a/chrome/browser/extensions/extension_function_dispatcher.cc
+++ b/chrome/browser/extensions/extension_function_dispatcher.cc
@@ -341,7 +341,7 @@ ExtensionFunctionDispatcher* ExtensionFunctionDispatcher::Create(
   if (!service->ExtensionBindingsAllowed(url))
     return NULL;
 
-  Extension* extension = service->GetExtensionByURL(url);
+  const Extension* extension = service->GetExtensionByURL(url);
   if (!extension)
     extension = service->GetExtensionByWebExtent(url);
 
@@ -355,7 +355,7 @@ ExtensionFunctionDispatcher* ExtensionFunctionDispatcher::Create(
 ExtensionFunctionDispatcher::ExtensionFunctionDispatcher(
     RenderViewHost* render_view_host,
     Delegate* delegate,
-    Extension* extension,
+    const Extension* extension,
     const GURL& url)
   : profile_(render_view_host->process()->profile()),
     render_view_host_(render_view_host),
@@ -448,7 +448,7 @@ void ExtensionFunctionDispatcher::HandleRequest(
   function->set_user_gesture(params.user_gesture);
   ExtensionsService* service = profile()->GetExtensionsService();
   DCHECK(service);
-  Extension* extension = service->GetExtensionById(extension_id(), false);
+  const Extension* extension = service->GetExtensionById(extension_id(), false);
   DCHECK(extension);
   function->set_include_incognito(service->IsIncognitoEnabled(extension) &&
                                   !extension->incognito_split_mode());
diff --git a/chrome/browser/extensions/extension_function_dispatcher.h b/chrome/browser/extensions/extension_function_dispatcher.h
index 99328f7..9969b1f 100644
--- a/chrome/browser/extensions/extension_function_dispatcher.h
+++ b/chrome/browser/extensions/extension_function_dispatcher.h
@@ -125,7 +125,7 @@ class ExtensionFunctionDispatcher {
  private:
   ExtensionFunctionDispatcher(RenderViewHost* render_view_host,
                               Delegate* delegate,
-                              Extension* extension,
+                              const Extension* extension,
                               const GURL& url);
 
   // We need to keep a pointer to the profile because we use it in the dtor
diff --git a/chrome/browser/extensions/extension_gallery_install_apitest.cc b/chrome/browser/extensions/extension_gallery_install_apitest.cc
index cf10ed4..5dd4811 100644
--- a/chrome/browser/extensions/extension_gallery_install_apitest.cc
+++ b/chrome/browser/extensions/extension_gallery_install_apitest.cc
@@ -24,8 +24,7 @@ class ExtensionGalleryInstallApiTest : public ExtensionApiTest {
 #else
 #define MAYBE_InstallAndUninstall InstallAndUninstall
 #endif
-IN_PROC_BROWSER_TEST_F(ExtensionGalleryInstallApiTest,
-                       MAYBE_InstallAndUninstall) {
+IN_PROC_BROWSER_TEST_F(ExtensionGalleryInstallApiTest, InstallAndUninstall) {
   host_resolver()->AddRule("www.example.com", "127.0.0.1");
   ASSERT_TRUE(test_server()->Start());
 
diff --git a/chrome/browser/extensions/extension_host.cc b/chrome/browser/extensions/extension_host.cc
index d39bcf7..0453880 100644
--- a/chrome/browser/extensions/extension_host.cc
+++ b/chrome/browser/extensions/extension_host.cc
@@ -122,8 +122,10 @@ class ExtensionHost::ProcessCreationQueue {
 ////////////////
 // ExtensionHost
 
-ExtensionHost::ExtensionHost(Extension* extension, SiteInstance* site_instance,
-                             const GURL& url, ViewType::Type host_type)
+ExtensionHost::ExtensionHost(const Extension* extension,
+                             SiteInstance* site_instance,
+                             const GURL& url,
+                             ViewType::Type host_type)
     : extension_(extension),
       profile_(site_instance->browsing_instance()->profile()),
       did_stop_loading_(false),
@@ -265,7 +267,7 @@ void ExtensionHost::Observe(NotificationType type,
       // sent. NULL it out so that dirty pointer issues don't arise in cases
       // when multiple ExtensionHost objects pointing to the same Extension are
       // present.
-      if (extension_ == Details<Extension>(details).ptr())
+      if (extension_ == Details<const Extension>(details).ptr())
         extension_ = NULL;
       break;
     default:
diff --git a/chrome/browser/extensions/extension_host.h b/chrome/browser/extensions/extension_host.h
index cf677e3..bb96c5d 100644
--- a/chrome/browser/extensions/extension_host.h
+++ b/chrome/browser/extensions/extension_host.h
@@ -51,7 +51,7 @@ class ExtensionHost : public RenderViewHostDelegate,
   typedef std::list<ExtensionHost*> HostPointerList;
   static HostPointerList* recently_deleted();
 
-  ExtensionHost(Extension* extension, SiteInstance* site_instance,
+  ExtensionHost(const Extension* extension, SiteInstance* site_instance,
                 const GURL& url, ViewType::Type host_type);
   ~ExtensionHost();
 
@@ -73,7 +73,7 @@ class ExtensionHost : public RenderViewHostDelegate,
   // instantiate Browser objects.
   void CreateView(Browser* browser);
 
-  Extension* extension() { return extension_; }
+  const Extension* extension() { return extension_; }
   RenderViewHost* render_view_host() const { return render_view_host_; }
   RenderProcessHost* render_process_host() const;
   SiteInstance* site_instance() const;
@@ -238,7 +238,7 @@ class ExtensionHost : public RenderViewHostDelegate,
   bool is_background_page() const { return !view(); }
 
   // The extension that we're hosting in this view.
-  Extension* extension_;
+  const Extension* extension_;
 
   // The profile that this host is tied to.
   Profile* profile_;
diff --git a/chrome/browser/extensions/extension_host_mac.h b/chrome/browser/extensions/extension_host_mac.h
index 65aceaa..da46f16 100644
--- a/chrome/browser/extensions/extension_host_mac.h
+++ b/chrome/browser/extensions/extension_host_mac.h
@@ -12,7 +12,7 @@ class RenderWidgetHostView;
 
 class ExtensionHostMac : public ExtensionHost {
  public:
-  ExtensionHostMac(Extension* extension, SiteInstance* site_instance,
+  ExtensionHostMac(const Extension* extension, SiteInstance* site_instance,
                    const GURL& url, ViewType::Type host_type) :
       ExtensionHost(extension, site_instance, url, host_type) {}
   virtual ~ExtensionHostMac();
diff --git a/chrome/browser/extensions/extension_icon_manager.cc b/chrome/browser/extensions/extension_icon_manager.cc
index 53c8923..887dc3ff 100644
--- a/chrome/browser/extensions/extension_icon_manager.cc
+++ b/chrome/browser/extensions/extension_icon_manager.cc
@@ -45,7 +45,7 @@ ExtensionIconManager::ExtensionIconManager()
 ExtensionIconManager::~ExtensionIconManager() {
 }
 
-void ExtensionIconManager::LoadIcon(Extension* extension) {
+void ExtensionIconManager::LoadIcon(const Extension* extension) {
   ExtensionResource icon_resource = extension->GetIconResource(
       Extension::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 876f5e0..cc0deb9 100644
--- a/chrome/browser/extensions/extension_icon_manager.h
+++ b/chrome/browser/extensions/extension_icon_manager.h
@@ -23,7 +23,7 @@ class ExtensionIconManager : public ImageLoadingTracker::Observer {
   virtual ~ExtensionIconManager();
 
   // Start loading the icon for the given extension.
-  void LoadIcon(Extension* extension);
+  void LoadIcon(const 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_infobar_delegate.cc b/chrome/browser/extensions/extension_infobar_delegate.cc
index b3b8a39..0aea7ce 100644
--- a/chrome/browser/extensions/extension_infobar_delegate.cc
+++ b/chrome/browser/extensions/extension_infobar_delegate.cc
@@ -15,7 +15,7 @@
 
 ExtensionInfoBarDelegate::ExtensionInfoBarDelegate(Browser* browser,
                                                    TabContents* tab_contents,
-                                                   Extension* extension,
+                                                   const Extension* extension,
                                                    const GURL& url)
     : InfoBarDelegate(tab_contents),
       observer_(NULL),
@@ -78,7 +78,7 @@ void ExtensionInfoBarDelegate::Observe(NotificationType type,
       break;
     }
     case NotificationType::EXTENSION_UNLOADED: {
-      Extension* extension = Details<Extension>(details).ptr();
+      const Extension* extension = Details<const Extension>(details).ptr();
       if (extension_ == extension)
         tab_contents_->RemoveInfoBar(this);
       break;
diff --git a/chrome/browser/extensions/extension_infobar_delegate.h b/chrome/browser/extensions/extension_infobar_delegate.h
index dae7aa9..949b655 100644
--- a/chrome/browser/extensions/extension_infobar_delegate.h
+++ b/chrome/browser/extensions/extension_infobar_delegate.h
@@ -28,10 +28,10 @@ class ExtensionInfoBarDelegate : public InfoBarDelegate,
   };
 
   ExtensionInfoBarDelegate(Browser* browser, TabContents* contents,
-                           Extension* extension, const GURL& url);
+                           const Extension* extension, const GURL& url);
   ~ExtensionInfoBarDelegate();
 
-  Extension* extension() { return extension_; }
+  const Extension* extension() { return extension_; }
   ExtensionHost* extension_host() { return extension_host_.get(); }
 
   void set_observer(DelegateObserver* observer) { observer_ = observer; }
@@ -60,7 +60,7 @@ class ExtensionInfoBarDelegate : public InfoBarDelegate,
   // The observer monitoring when the delegate dies.
   DelegateObserver* observer_;
 
-  Extension* extension_;
+  const Extension* extension_;
 
   TabContents* tab_contents_;
 
diff --git a/chrome/browser/extensions/extension_infobar_module.cc b/chrome/browser/extensions/extension_infobar_module.cc
index 590bfc1..6662bea 100644
--- a/chrome/browser/extensions/extension_infobar_module.cc
+++ b/chrome/browser/extensions/extension_infobar_module.cc
@@ -32,7 +32,7 @@ bool ShowInfoBarFunction::RunImpl() {
   std::string html_path;
   EXTENSION_FUNCTION_VALIDATE(args->GetString(keys::kHtmlPath, &html_path));
 
-  Extension* extension = GetExtension();
+  const Extension* extension = GetExtension();
   GURL url = extension->GetResourceURL(extension->url(), html_path);
 
   Browser* browser = NULL;
diff --git a/chrome/browser/extensions/extension_install_ui.cc b/chrome/browser/extensions/extension_install_ui.cc
index b1b2205..3c5f819 100644
--- a/chrome/browser/extensions/extension_install_ui.cc
+++ b/chrome/browser/extensions/extension_install_ui.cc
@@ -82,7 +82,7 @@ ExtensionInstallUI::~ExtensionInstallUI() {
 }
 
 void ExtensionInstallUI::ConfirmInstall(Delegate* delegate,
-                                        Extension* extension) {
+                                        const Extension* extension) {
   DCHECK(ui_loop_ == MessageLoop::current());
   extension_ = extension;
   delegate_ = delegate;
@@ -92,7 +92,7 @@ void ExtensionInstallUI::ConfirmInstall(Delegate* delegate,
   // to allow the user to revert if they don't like it.
   if (extension->is_theme()) {
     // Remember the current theme in case the user pressed undo.
-    Extension* previous_theme = profile_->GetTheme();
+    const Extension* previous_theme = profile_->GetTheme();
     if (previous_theme)
       previous_theme_id_ = previous_theme->id();
 
@@ -113,7 +113,7 @@ void ExtensionInstallUI::ConfirmInstall(Delegate* delegate,
 }
 
 void ExtensionInstallUI::ConfirmUninstall(Delegate* delegate,
-                                          Extension* extension) {
+                                          const Extension* extension) {
   DCHECK(ui_loop_ == MessageLoop::current());
   extension_ = extension;
   delegate_ = delegate;
@@ -121,7 +121,7 @@ void ExtensionInstallUI::ConfirmUninstall(Delegate* delegate,
   ShowConfirmation(UNINSTALL_PROMPT);
 }
 
-void ExtensionInstallUI::OnInstallSuccess(Extension* extension) {
+void ExtensionInstallUI::OnInstallSuccess(const Extension* extension) {
   if (extension->is_theme()) {
     ShowThemeInfoBar(previous_theme_id_, previous_use_system_theme_,
                      extension, profile_);
@@ -226,7 +226,7 @@ void ExtensionInstallUI::OnImageLoaded(
 
 void ExtensionInstallUI::ShowThemeInfoBar(
     const std::string& previous_theme_id, bool previous_use_system_theme,
-    Extension* new_theme, Profile* profile) {
+    const Extension* new_theme, Profile* profile) {
   if (!new_theme->is_theme())
     return;
 
@@ -283,7 +283,7 @@ void ExtensionInstallUI::ShowConfirmation(PromptType prompt_type) {
 
 #if defined(OS_MACOSX)
 void ExtensionInstallUI::ShowGenericExtensionInstalledInfoBar(
-    Extension* new_extension) {
+    const Extension* new_extension) {
   Browser* browser = BrowserList::GetLastActiveWithProfile(profile_);
   if (!browser)
     return;
@@ -304,7 +304,7 @@ void ExtensionInstallUI::ShowGenericExtensionInstalledInfoBar(
 #endif
 
 InfoBarDelegate* ExtensionInstallUI::GetNewThemeInstalledInfoBarDelegate(
-    TabContents* tab_contents, Extension* new_theme,
+    TabContents* tab_contents, const Extension* new_theme,
     const std::string& previous_theme_id, bool previous_use_system_theme) {
 #if defined(TOOLKIT_GTK)
   return new GtkThemeInstalledInfoBarDelegate(tab_contents, new_theme,
diff --git a/chrome/browser/extensions/extension_install_ui.h b/chrome/browser/extensions/extension_install_ui.h
index 7ab2c02..6cc8876 100644
--- a/chrome/browser/extensions/extension_install_ui.h
+++ b/chrome/browser/extensions/extension_install_ui.h
@@ -58,17 +58,17 @@ class ExtensionInstallUI : public ImageLoadingTracker::Observer {
   //
   // We *MUST* eventually call either Proceed() or Abort()
   // on |delegate|.
-  virtual void ConfirmInstall(Delegate* delegate, Extension* extension);
+  virtual void ConfirmInstall(Delegate* delegate, const Extension* extension);
 
   // This is called by the extensions management page to verify whether the
   // uninstallation should proceed. This is declared virtual for testing.
   //
   // We *MUST* eventually call either Proceed() or Abort()
   // on |delegate|.
-  virtual void ConfirmUninstall(Delegate* delegate, Extension* extension);
+  virtual void ConfirmUninstall(Delegate* delegate, const Extension* extension);
 
   // Installation was successful. This is declared virtual for testing.
-  virtual void OnInstallSuccess(Extension* extension);
+  virtual void OnInstallSuccess(const Extension* extension);
 
   // Installation failed. This is declared virtual for testing.
   virtual void OnInstallFailure(const std::string& error);
@@ -85,7 +85,7 @@ class ExtensionInstallUI : public ImageLoadingTracker::Observer {
   // GetNewThemeInstalledInfoBarDelegate()).
   static void ShowThemeInfoBar(
       const std::string& previous_theme_id, bool previous_use_system_theme,
-      Extension* new_theme, Profile* profile);
+      const Extension* new_theme, Profile* profile);
 
  private:
   // Starts the process of showing a confirmation UI, which is split into two.
@@ -96,25 +96,25 @@ class ExtensionInstallUI : public ImageLoadingTracker::Observer {
 #if defined(OS_MACOSX)
   // When an extension is installed on Mac with neither browser action nor
   // page action icons, show an infobar instead of a popup bubble.
-  void ShowGenericExtensionInstalledInfoBar(Extension* new_extension);
+  void ShowGenericExtensionInstalledInfoBar(const Extension* new_extension);
 #endif
 
   // Returns the delegate to control the browser's info bar. This is
   // within its own function due to its platform-specific nature.
   static InfoBarDelegate* GetNewThemeInstalledInfoBarDelegate(
-      TabContents* tab_contents, Extension* new_theme,
+      TabContents* tab_contents, const Extension* new_theme,
       const std::string& previous_theme_id, bool previous_use_system_theme);
 
   // Implements the showing of the install/uninstall dialog prompt.
   // NOTE: The implementations of this function is platform-specific.
   static void ShowExtensionInstallUIPromptImpl(
-      Profile* profile, Delegate* delegate, Extension* extension,
+      Profile* profile, Delegate* delegate, const Extension* extension,
       SkBitmap* icon, PromptType type);
 
   // Implements the showing of the new install dialog. The implementations of
   // this function are platform-specific.
   static void ShowExtensionInstallUIPrompt2Impl(
-      Profile* profile, Delegate* delegate, Extension* extension,
+      Profile* profile, Delegate* delegate, const Extension* extension,
       SkBitmap* icon, const std::vector<string16>& permissions);
 
   Profile* profile_;
@@ -125,7 +125,7 @@ class ExtensionInstallUI : public ImageLoadingTracker::Observer {
   bool previous_use_system_theme_;
 
   SkBitmap icon_;  // The extensions installation icon.
-  Extension* extension_;  // The extension we are showing the UI for.
+  const Extension* extension_;  // The extension we are showing the UI for.
   Delegate* delegate_;    // The delegate we will call Proceed/Abort on after
                           // confirmation UI.
   PromptType prompt_type_;  // The type of prompt we are going to show.
diff --git a/chrome/browser/extensions/extension_install_ui_browsertest.cc b/chrome/browser/extensions/extension_install_ui_browsertest.cc
index 14a6a5b..9a5a9f2 100644
--- a/chrome/browser/extensions/extension_install_ui_browsertest.cc
+++ b/chrome/browser/extensions/extension_install_ui_browsertest.cc
@@ -39,7 +39,7 @@ IN_PROC_BROWSER_TEST_F(ExtensionInstallUIBrowserTest,
   // Install theme once and undo to verify we go back to default theme.
   FilePath theme_path = test_data_dir_.AppendASCII("theme.crx");
   ASSERT_TRUE(InstallExtensionWithUI(theme_path, 1));
-  Extension* theme = browser()->profile()->GetTheme();
+  const Extension* theme = browser()->profile()->GetTheme();
   ASSERT_TRUE(theme);
   ASSERT_EQ(theme_crx, theme->id());
   VerifyThemeInfoBarAndUndoInstall();
diff --git a/chrome/browser/extensions/extension_management_api.cc b/chrome/browser/extensions/extension_management_api.cc
index 50777db..fcf40b8 100644
--- a/chrome/browser/extensions/extension_management_api.cc
+++ b/chrome/browser/extensions/extension_management_api.cc
@@ -107,7 +107,7 @@ bool GetAllExtensionsFunction::RunImpl() {
 bool LaunchAppFunction::RunImpl() {
   std::string extension_id;
   EXTENSION_FUNCTION_VALIDATE(args_->GetString(0, &extension_id));
-  Extension* extension = service()->GetExtensionById(extension_id, true);
+  const Extension* extension = service()->GetExtensionById(extension_id, true);
   if (!extension) {
     error_ = ExtensionErrorUtils::FormatErrorMessage(kNoExtensionError,
                                                      extension_id);
@@ -219,7 +219,7 @@ void ExtensionManagementEventRouter::Observe(
         Details<UninstalledExtensionInfo>(details).ptr()->extension_id;
     args.Append(Value::CreateStringValue(extension_id));
   } else {
-    Extension* extension = Details<Extension>(details).ptr();
+    const Extension* extension = Details<const Extension>(details).ptr();
     CHECK(extension);
     ExtensionsService* service = profile->GetExtensionsService();
     bool enabled = service->GetExtensionById(extension->id(), false) != NULL;
diff --git a/chrome/browser/extensions/extension_management_browsertest.cc b/chrome/browser/extensions/extension_management_browsertest.cc
index e6b1f8f..a80cc8a 100644
--- a/chrome/browser/extensions/extension_management_browsertest.cc
+++ b/chrome/browser/extensions/extension_management_browsertest.cc
@@ -25,7 +25,7 @@ class ExtensionManagementTest : public ExtensionBrowserTest {
   // in the extension's manifest. We use the version as reported by the
   // background page to test how overinstalling crx files with the same
   // manifest version works.
-  bool IsExtensionAtVersion(Extension* extension,
+  bool IsExtensionAtVersion(const Extension* extension,
                             const std::string& expected_version) {
     // Test that the extension's version from the manifest and reported by the
     // background page is correct.  This is to ensure that the processes are in
@@ -171,7 +171,7 @@ IN_PROC_BROWSER_TEST_F(ExtensionManagementTest, DisableEnable) {
                     .AppendASCII("1.0")));
   ASSERT_EQ(size_before + 1, service->extensions()->size());
   EXPECT_EQ(0u, service->disabled_extensions()->size());
-  Extension* extension = service->extensions()->at(size_before);
+  const Extension* extension = service->extensions()->at(size_before);
   EXPECT_TRUE(manager->GetBackgroundHostForExtension(extension));
   ASSERT_TRUE(service->HasInstalledExtensions());
 
diff --git a/chrome/browser/extensions/extension_menu_manager.cc b/chrome/browser/extensions/extension_menu_manager.cc
index 58bd1af..9ddb0f0 100644
--- a/chrome/browser/extensions/extension_menu_manager.cc
+++ b/chrome/browser/extensions/extension_menu_manager.cc
@@ -125,7 +125,7 @@ const ExtensionMenuItem::List* ExtensionMenuManager::MenuItems(
   return NULL;
 }
 
-bool ExtensionMenuManager::AddContextItem(Extension* extension,
+bool ExtensionMenuManager::AddContextItem(const 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
@@ -455,7 +455,7 @@ void ExtensionMenuManager::Observe(NotificationType type,
     NOTREACHED();
     return;
   }
-  Extension* extension = Details<Extension>(details).ptr();
+  const Extension* extension = Details<const Extension>(details).ptr();
   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 41edb61..4455ee1 100644
--- a/chrome/browser/extensions/extension_menu_manager.h
+++ b/chrome/browser/extensions/extension_menu_manager.h
@@ -198,7 +198,7 @@ class ExtensionMenuManager : public 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(Extension* extension, ExtensionMenuItem* item);
+  bool AddContextItem(const 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 56c95c4..549c245 100644
--- a/chrome/browser/extensions/extension_menu_manager_unittest.cc
+++ b/chrome/browser/extensions/extension_menu_manager_unittest.cc
@@ -323,7 +323,7 @@ TEST_F(ExtensionMenuManagerTest, ExtensionUnloadRemovesMenuItems) {
   // gone.
   notifier->Notify(NotificationType::EXTENSION_UNLOADED,
                    Source<Profile>(NULL),
-                   Details<Extension>(extension1));
+                   Details<const Extension>(extension1));
   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_metrics_apitest.cc b/chrome/browser/extensions/extension_metrics_apitest.cc
index ee4761c..c9464d2 100644
--- a/chrome/browser/extensions/extension_metrics_apitest.cc
+++ b/chrome/browser/extensions/extension_metrics_apitest.cc
@@ -146,7 +146,7 @@ IN_PROC_BROWSER_TEST_F(ExtensionApiTest, Metrics) {
   UserActionObserver observer;
 
   ASSERT_TRUE(RunExtensionTest("metrics")) << message_;
-  Extension* extension = GetSingleLoadedExtension();
+  const Extension* extension = GetSingleLoadedExtension();
   ASSERT_TRUE(extension);
 
   observer.ValidateUserActions(extension,
diff --git a/chrome/browser/extensions/extension_pref_store.cc b/chrome/browser/extensions/extension_pref_store.cc
index 773e94e..27719ed 100644
--- a/chrome/browser/extensions/extension_pref_store.cc
+++ b/chrome/browser/extensions/extension_pref_store.cc
@@ -25,7 +25,7 @@ ExtensionPrefStore::~ExtensionPrefStore() {
   notification_registrar_.RemoveAll();
 }
 
-void ExtensionPrefStore::InstallExtensionPref(Extension* extension,
+void ExtensionPrefStore::InstallExtensionPref(const Extension* extension,
                                               const char* new_pref_path,
                                               Value* new_pref_value) {
   ExtensionStack::iterator i;
@@ -62,7 +62,7 @@ void ExtensionPrefStore::InstallExtensionPref(Extension* extension,
   UpdateOnePref(new_pref_path);
 }
 
-void ExtensionPrefStore::UninstallExtension(Extension* extension) {
+void ExtensionPrefStore::UninstallExtension(const Extension* extension) {
   // Remove this extension from the stack.
   for (ExtensionStack::iterator i = extension_stack_.begin();
       i != extension_stack_.end(); ++i) {
@@ -178,7 +178,7 @@ void ExtensionPrefStore::Observe(NotificationType type,
     }
     case NotificationType::EXTENSION_UNLOADED: {
       Profile* extension_profile = Source<Profile>(source).ptr();
-      Extension* extension = Details<Extension>(details).ptr();
+      const Extension* extension = Details<const Extension>(details).ptr();
       // The ExtensionPrefStore for the local state watches all profiles.
       if (profile_ == NULL || profile_ == extension_profile)
         UninstallExtension(extension);
@@ -190,7 +190,7 @@ void ExtensionPrefStore::Observe(NotificationType type,
   }
 }
 
-ExtensionPrefStore::ExtensionPrefs::ExtensionPrefs(Extension* extension,
+ExtensionPrefStore::ExtensionPrefs::ExtensionPrefs(const Extension* extension,
     PrefValueMap* values) : extension(extension), pref_values(values) {}
 
 ExtensionPrefStore::ExtensionPrefs::~ExtensionPrefs() {
diff --git a/chrome/browser/extensions/extension_pref_store.h b/chrome/browser/extensions/extension_pref_store.h
index 926f29e..00248c3 100644
--- a/chrome/browser/extensions/extension_pref_store.h
+++ b/chrome/browser/extensions/extension_pref_store.h
@@ -39,13 +39,13 @@ class ExtensionPrefStore : public PrefStore,
   // Begins tracking the preference and value an extension wishes to set. This
   // must be called each time an extension API tries to set a preference.
   // The ExtensionPrefStore will take ownership of the |pref_value|.
-  virtual void InstallExtensionPref(Extension* extension,
+  virtual void InstallExtensionPref(const Extension* extension,
                                     const char* pref_path,
                                     Value* pref_value);
 
   // Removes an extension and all its preference settings from this PrefStore.
   // This must be called when an extension is uninstalled or disabled.
-  virtual void UninstallExtension(Extension* extension);
+  virtual void UninstallExtension(const Extension* extension);
 
   // PrefStore methods:
   virtual DictionaryValue* prefs() { return prefs_.get(); }
@@ -56,7 +56,7 @@ class ExtensionPrefStore : public PrefStore,
   // The nested pairs are <extension, <pref_path, pref_value> >. This is here,
   // rather than in (say) notification_type.h, to keep the dependency on
   // std::pair out of the many places that include notification_type.h.
-  typedef std::pair<Extension*, std::pair<const char*, Value*> >
+  typedef std::pair<const Extension*, std::pair<const char*, Value*> >
       ExtensionPrefDetails;
 
  protected:
@@ -95,10 +95,10 @@ class ExtensionPrefStore : public PrefStore,
 
   // Associates an extension with the prefs it sets. Owns the pref values.
   struct ExtensionPrefs {
-    ExtensionPrefs(Extension* extension, PrefValueMap* values);
+    ExtensionPrefs(const Extension* extension, PrefValueMap* values);
     ~ExtensionPrefs();
 
-    Extension* extension;
+    const Extension* extension;
     PrefValueMap* pref_values;
   };
 
diff --git a/chrome/browser/extensions/extension_prefs.cc b/chrome/browser/extensions/extension_prefs.cc
index eb6485f..8fbabf6 100644
--- a/chrome/browser/extensions/extension_prefs.cc
+++ b/chrome/browser/extensions/extension_prefs.cc
@@ -320,7 +320,7 @@ bool ExtensionPrefs::DidExtensionEscalatePermissions(
 }
 
 void ExtensionPrefs::SetDidExtensionEscalatePermissions(
-    Extension* extension, bool did_escalate) {
+    const Extension* extension, bool did_escalate) {
   UpdateExtensionPref(extension->id(), kExtensionDidEscalatePermissions,
                       Value::CreateBooleanValue(did_escalate));
   prefs_->ScheduleSavePersistentPrefs();
@@ -518,7 +518,7 @@ void ExtensionPrefs::SetToolbarOrder(
 }
 
 void ExtensionPrefs::OnExtensionInstalled(
-    Extension* extension, Extension::State initial_state,
+    const Extension* extension, Extension::State initial_state,
     bool initial_incognito_enabled) {
   const std::string& id = extension->id();
   UpdateExtensionPref(id, kPrefState,
@@ -575,7 +575,7 @@ Extension::State ExtensionPrefs::GetExtensionState(
   return static_cast<Extension::State>(state);
 }
 
-void ExtensionPrefs::SetExtensionState(Extension* extension,
+void ExtensionPrefs::SetExtensionState(const Extension* extension,
                                        Extension::State state) {
   UpdateExtensionPref(extension->id(), kPrefState,
                       Value::CreateIntegerValue(state));
@@ -596,7 +596,7 @@ std::string ExtensionPrefs::GetVersionString(const std::string& extension_id) {
   return version;
 }
 
-void ExtensionPrefs::UpdateManifest(Extension* extension) {
+void ExtensionPrefs::UpdateManifest(const Extension* extension) {
   if (extension->location() != Extension::LOAD) {
     UpdateExtensionPref(extension->id(), kPrefManifest,
                         extension->manifest_value()->DeepCopy());
diff --git a/chrome/browser/extensions/extension_prefs.h b/chrome/browser/extensions/extension_prefs.h
index 97547ea..eb16329 100644
--- a/chrome/browser/extensions/extension_prefs.h
+++ b/chrome/browser/extensions/extension_prefs.h
@@ -63,7 +63,7 @@ class ExtensionPrefs {
   void SetToolbarOrder(const std::vector<std::string>& extension_ids);
 
   // Called when an extension is installed, so that prefs get created.
-  void OnExtensionInstalled(Extension* extension,
+  void OnExtensionInstalled(const Extension* extension,
                             Extension::State initial_state,
                             bool initial_incognito_enabled);
 
@@ -76,14 +76,14 @@ class ExtensionPrefs {
   Extension::State GetExtensionState(const std::string& extension_id);
 
   // Called to change the extension's state when it is enabled/disabled.
-  void SetExtensionState(Extension* extension, Extension::State);
+  void SetExtensionState(const Extension* extension, Extension::State);
 
   // 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(Extension* extension,
+  void SetDidExtensionEscalatePermissions(const Extension* extension,
                                           bool did_escalate);
 
   // Returns the version string for the currently installed extension, or
@@ -92,7 +92,7 @@ class ExtensionPrefs {
 
   // Re-writes the extension manifest into the prefs.
   // Called to change the extension's manifest when it's re-localized.
-  void UpdateManifest(Extension* extension);
+  void UpdateManifest(const Extension* extension);
 
   // Returns extension path based on extension ID, or empty FilePath on error.
   FilePath GetExtensionPath(const std::string& extension_id);
diff --git a/chrome/browser/extensions/extension_process_manager.cc b/chrome/browser/extensions/extension_process_manager.cc
index f941544..12ff5c0 100644
--- a/chrome/browser/extensions/extension_process_manager.cc
+++ b/chrome/browser/extensions/extension_process_manager.cc
@@ -32,11 +32,12 @@ class IncognitoExtensionProcessManager : public ExtensionProcessManager {
  public:
   explicit IncognitoExtensionProcessManager(Profile* profile);
   virtual ~IncognitoExtensionProcessManager() {}
-  virtual ExtensionHost* CreateView(Extension* extension,
+  virtual ExtensionHost* CreateView(const Extension* extension,
                                     const GURL& url,
                                     Browser* browser,
                                     ViewType::Type view_type);
-  virtual void CreateBackgroundHost(Extension* extension, const GURL& url);
+  virtual void CreateBackgroundHost(const Extension* extension,
+                                    const GURL& url);
   virtual SiteInstance* GetSiteInstanceForURL(const GURL& url);
   virtual RenderProcessHost* GetExtensionProcess(const GURL& url);
 
@@ -48,7 +49,7 @@ class IncognitoExtensionProcessManager : public ExtensionProcessManager {
 
   // Returns the extension for an URL, which can either be a chrome-extension
   // URL or a web app URL.
-  Extension* GetExtensionOrAppByURL(const GURL& url);
+  const Extension* GetExtensionOrAppByURL(const GURL& url);
 
   // Returns true if the extension is allowed to run in incognito mode.
   bool IsIncognitoEnabled(const Extension* extension);
@@ -57,7 +58,7 @@ class IncognitoExtensionProcessManager : public ExtensionProcessManager {
 };
 
 static void CreateBackgroundHost(
-    ExtensionProcessManager* manager, Extension* extension) {
+    ExtensionProcessManager* manager, const Extension* extension) {
   // Start the process for the master page, if it exists.
   if (extension->background_url().is_valid())
     manager->CreateBackgroundHost(extension, extension->background_url());
@@ -110,7 +111,7 @@ ExtensionProcessManager::~ExtensionProcessManager() {
   DCHECK(background_hosts_.empty());
 }
 
-ExtensionHost* ExtensionProcessManager::CreateView(Extension* extension,
+ExtensionHost* ExtensionProcessManager::CreateView(const Extension* extension,
                                                    const GURL& url,
                                                    Browser* browser,
                                                    ViewType::Type view_type) {
@@ -137,14 +138,14 @@ ExtensionHost* ExtensionProcessManager::CreateView(const GURL& url,
   ExtensionsService* service =
       browsing_instance_->profile()->GetExtensionsService();
   if (service) {
-    Extension* extension = service->GetExtensionByURL(url);
+    const Extension* extension = service->GetExtensionByURL(url);
     if (extension)
       return CreateView(extension, url, browser, view_type);
   }
   return NULL;
 }
 
-ExtensionHost* ExtensionProcessManager::CreatePopup(Extension* extension,
+ExtensionHost* ExtensionProcessManager::CreatePopup(const Extension* extension,
                                                     const GURL& url,
                                                     Browser* browser) {
   return CreateView(extension, url, browser, ViewType::EXTENSION_POPUP);
@@ -155,9 +156,8 @@ ExtensionHost* ExtensionProcessManager::CreatePopup(const GURL& url,
   return CreateView(url, browser, ViewType::EXTENSION_POPUP);
 }
 
-ExtensionHost* ExtensionProcessManager::CreateInfobar(Extension* extension,
-                                                      const GURL& url,
-                                                      Browser* browser) {
+ExtensionHost* ExtensionProcessManager::CreateInfobar(
+    const Extension* extension, const GURL& url, Browser* browser) {
   return CreateView(extension, url, browser, ViewType::EXTENSION_INFOBAR);
 }
 
@@ -167,7 +167,7 @@ ExtensionHost* ExtensionProcessManager::CreateInfobar(const GURL& url,
 }
 
 void ExtensionProcessManager::CreateBackgroundHost(
-    Extension* extension, const GURL& url) {
+    const Extension* extension, const GURL& url) {
   // Don't create multiple background hosts for an extension.
   if (GetBackgroundHostForExtension(extension))
     return;
@@ -185,7 +185,7 @@ void ExtensionProcessManager::CreateBackgroundHost(
   OnExtensionHostCreated(host, true);
 }
 
-void ExtensionProcessManager::OpenOptionsPage(Extension* extension,
+void ExtensionProcessManager::OpenOptionsPage(const Extension* extension,
                                               Browser* browser) {
   DCHECK(!extension->options_url().is_empty());
 
@@ -203,7 +203,7 @@ void ExtensionProcessManager::OpenOptionsPage(Extension* extension,
 }
 
 ExtensionHost* ExtensionProcessManager::GetBackgroundHostForExtension(
-    Extension* extension) {
+    const Extension* extension) {
   for (ExtensionHostSet::iterator iter = background_hosts_.begin();
        iter != background_hosts_.end(); ++iter) {
     ExtensionHost* host = *iter;
@@ -230,7 +230,7 @@ void ExtensionProcessManager::RegisterExtensionProcess(
       browsing_instance_->profile()->GetExtensionsService();
 
   std::vector<std::string> page_action_ids;
-  Extension* extension =
+  const Extension* extension =
       extension_service->GetExtensionById(extension_id, false);
   if (extension->page_action())
     page_action_ids.push_back(extension->page_action()->id());
@@ -288,14 +288,14 @@ void ExtensionProcessManager::Observe(NotificationType type,
       ExtensionsService* service =
           Source<Profile>(source).ptr()->GetExtensionsService();
       if (service->is_ready()) {
-        Extension* extension = Details<Extension>(details).ptr();
+        const Extension* extension = Details<const Extension>(details).ptr();
         ::CreateBackgroundHost(this, extension);
       }
       break;
     }
 
     case NotificationType::EXTENSION_UNLOADED: {
-      Extension* extension = Details<Extension>(details).ptr();
+      const Extension* extension = Details<const Extension>(details).ptr();
       for (ExtensionHostSet::iterator iter = background_hosts_.begin();
            iter != background_hosts_.end(); ++iter) {
         ExtensionHost* host = *iter;
@@ -374,7 +374,7 @@ IncognitoExtensionProcessManager::IncognitoExtensionProcessManager(
 }
 
 ExtensionHost* IncognitoExtensionProcessManager::CreateView(
-    Extension* extension,
+    const Extension* extension,
     const GURL& url,
     Browser* browser,
     ViewType::Type view_type) {
@@ -394,7 +394,7 @@ ExtensionHost* IncognitoExtensionProcessManager::CreateView(
 }
 
 void IncognitoExtensionProcessManager::CreateBackgroundHost(
-    Extension* extension, const GURL& url) {
+    const Extension* extension, const GURL& url) {
   if (extension->incognito_split_mode()) {
     if (IsIncognitoEnabled(extension))
       ExtensionProcessManager::CreateBackgroundHost(extension, url);
@@ -406,7 +406,7 @@ void IncognitoExtensionProcessManager::CreateBackgroundHost(
 
 SiteInstance* IncognitoExtensionProcessManager::GetSiteInstanceForURL(
     const GURL& url) {
-  Extension* extension = GetExtensionOrAppByURL(url);
+  const Extension* extension = GetExtensionOrAppByURL(url);
   if (!extension || extension->incognito_split_mode()) {
     return ExtensionProcessManager::GetSiteInstanceForURL(url);
   } else {
@@ -416,7 +416,7 @@ SiteInstance* IncognitoExtensionProcessManager::GetSiteInstanceForURL(
 
 RenderProcessHost* IncognitoExtensionProcessManager::GetExtensionProcess(
     const GURL& url) {
-  Extension* extension = GetExtensionOrAppByURL(url);
+  const Extension* extension = GetExtensionOrAppByURL(url);
   if (!extension || extension->incognito_split_mode()) {
     return ExtensionProcessManager::GetExtensionProcess(url);
   } else {
@@ -424,7 +424,7 @@ RenderProcessHost* IncognitoExtensionProcessManager::GetExtensionProcess(
   }
 }
 
-Extension* IncognitoExtensionProcessManager::GetExtensionOrAppByURL(
+const Extension* IncognitoExtensionProcessManager::GetExtensionOrAppByURL(
     const GURL& url) {
   ExtensionsService* service =
       browsing_instance_->profile()->GetExtensionsService();
diff --git a/chrome/browser/extensions/extension_process_manager.h b/chrome/browser/extensions/extension_process_manager.h
index d284275..2d812ef 100644
--- a/chrome/browser/extensions/extension_process_manager.h
+++ b/chrome/browser/extensions/extension_process_manager.h
@@ -35,33 +35,34 @@ class ExtensionProcessManager : public 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* CreateView(Extension* extension,
+  virtual ExtensionHost* CreateView(const Extension* extension,
                             const GURL& url,
                             Browser* browser,
                             ViewType::Type view_type);
   ExtensionHost* CreateView(const GURL& url,
                             Browser* browser,
                             ViewType::Type view_type);
-  ExtensionHost* CreatePopup(Extension* extension,
+  ExtensionHost* CreatePopup(const Extension* extension,
                              const GURL& url,
                              Browser* browser);
   ExtensionHost* CreatePopup(const GURL& url, Browser* browser);
-  ExtensionHost* CreateInfobar(Extension* extension,
+  ExtensionHost* CreateInfobar(const Extension* extension,
                                const GURL& url,
                                Browser* browser);
   ExtensionHost* CreateInfobar(const GURL& url,
                                Browser* browser);
 
   // Open the extension's options page.
-  void OpenOptionsPage(Extension* extension, Browser* browser);
+  void OpenOptionsPage(const Extension* extension, Browser* browser);
 
   // Creates a new UI-less extension instance.  Like CreateView, but not
   // displayed anywhere.
-  virtual void CreateBackgroundHost(Extension* extension, const GURL& url);
+  virtual void CreateBackgroundHost(const Extension* extension,
+                                    const GURL& url);
 
   // Gets the ExtensionHost for the background page for an extension, or NULL if
   // the extension isn't running or doesn't have a background page.
-  ExtensionHost* GetBackgroundHostForExtension(Extension* extension);
+  ExtensionHost* GetBackgroundHostForExtension(const Extension* extension);
 
   // Returns the SiteInstance that the given URL belongs to.
   virtual SiteInstance* GetSiteInstanceForURL(const GURL& url);
diff --git a/chrome/browser/extensions/extension_proxy_apitest.cc b/chrome/browser/extensions/extension_proxy_apitest.cc
index 9c127ad..a22baf8 100644
--- a/chrome/browser/extensions/extension_proxy_apitest.cc
+++ b/chrome/browser/extensions/extension_proxy_apitest.cc
@@ -16,7 +16,7 @@ IN_PROC_BROWSER_TEST_F(ExtensionApiTest, ProxyAutoSettings) {
       switches::kEnableExperimentalExtensionApis);
 
   ASSERT_TRUE(RunExtensionTest("proxy/auto")) << message_;
-  Extension* extension = GetSingleLoadedExtension();
+  const Extension* extension = GetSingleLoadedExtension();
   ASSERT_TRUE(extension);
 
   PrefService* pref_service = browser()->profile()->GetPrefs();
@@ -46,7 +46,7 @@ IN_PROC_BROWSER_TEST_F(ExtensionApiTest, ProxyManualSingle) {
       switches::kEnableExperimentalExtensionApis);
 
   ASSERT_TRUE(RunExtensionTest("proxy/single")) << message_;
-  Extension* extension = GetSingleLoadedExtension();
+  const Extension* extension = GetSingleLoadedExtension();
   ASSERT_TRUE(extension);
 
   PrefService* pref_service = browser()->profile()->GetPrefs();
@@ -81,7 +81,7 @@ IN_PROC_BROWSER_TEST_F(ExtensionApiTest, ProxyManualIndividual) {
       switches::kEnableExperimentalExtensionApis);
 
   ASSERT_TRUE(RunExtensionTest("proxy/individual")) << message_;
-  Extension* extension = GetSingleLoadedExtension();
+  const Extension* extension = GetSingleLoadedExtension();
   ASSERT_TRUE(extension);
 
   PrefService* pref_service = browser()->profile()->GetPrefs();
diff --git a/chrome/browser/extensions/extension_sidebar_api.cc b/chrome/browser/extensions/extension_sidebar_api.cc
index 8b6913e..7dbb6fd 100644
--- a/chrome/browser/extensions/extension_sidebar_api.cc
+++ b/chrome/browser/extensions/extension_sidebar_api.cc
@@ -51,7 +51,7 @@ const char kShownState[] = "shown";
 }
 
 static GURL ResolvePossiblyRelativeURL(const std::string& url_string,
-                                       Extension* extension) {
+                                       const Extension* extension) {
   GURL url = GURL(url_string);
   if (!url.is_valid())
     url = extension->GetResourceURL(url_string);
@@ -59,7 +59,7 @@ static GURL ResolvePossiblyRelativeURL(const std::string& url_string,
   return url;
 }
 
-static bool CanUseHost(Extension* extension,
+static bool CanUseHost(const Extension* extension,
                        const GURL& url,
                        std::string* error) {
   if (extension->HasHostPermission(url))
diff --git a/chrome/browser/extensions/extension_tabs_module.cc b/chrome/browser/extensions/extension_tabs_module.cc
index 76b001a..ce3a92a 100644
--- a/chrome/browser/extensions/extension_tabs_module.cc
+++ b/chrome/browser/extensions/extension_tabs_module.cc
@@ -65,7 +65,7 @@ static bool GetTabById(int tab_id, Profile* profile,
 // but because the api shipped with urls resolved relative to their extension
 // base, we decided it wasn't worth breaking existing extensions to fix.
 static GURL ResolvePossiblyRelativeURL(std::string url_string,
-                                       Extension* extension);
+                                       const Extension* extension);
 
 // Return the type name for a browser window type.
 static std::string GetWindowTypeText(Browser::Type type);
@@ -705,7 +705,7 @@ bool UpdateTabFunction::RunImpl() {
     // JavaScript URLs can do the same kinds of things as cross-origin XHR, so
     // we need to check host permissions before allowing them.
     if (url.SchemeIs(chrome::kJavaScriptScheme)) {
-      Extension* extension = GetExtension();
+      const Extension* extension = GetExtension();
       const std::vector<URLPattern> host_permissions =
           extension->host_permissions();
       if (!Extension::CanExecuteScriptOnPage(
@@ -1149,7 +1149,7 @@ static std::string GetWindowTypeText(Browser::Type type) {
 }
 
 static GURL ResolvePossiblyRelativeURL(std::string url_string,
-                                       Extension* extension) {
+                                       const Extension* extension) {
   GURL url = GURL(url_string);
   if (!url.is_valid())
     url = extension->GetResourceURL(url_string);
diff --git a/chrome/browser/extensions/extension_toolbar_model.cc b/chrome/browser/extensions/extension_toolbar_model.cc
index 086b8c4..4b55442 100644
--- a/chrome/browser/extensions/extension_toolbar_model.cc
+++ b/chrome/browser/extensions/extension_toolbar_model.cc
@@ -45,7 +45,7 @@ void ExtensionToolbarModel::RemoveObserver(Observer* observer) {
   observers_.RemoveObserver(observer);
 }
 
-void ExtensionToolbarModel::MoveBrowserAction(Extension* extension,
+void ExtensionToolbarModel::MoveBrowserAction(const Extension* extension,
                                               int index) {
   ExtensionList::iterator pos = std::find(begin(), end(), extension);
   if (pos == end()) {
@@ -93,7 +93,7 @@ void ExtensionToolbarModel::Observe(NotificationType type,
   if (!service_->is_ready())
     return;
 
-  Extension* extension = Details<Extension>(details).ptr();
+  const Extension* extension = Details<const Extension>(details).ptr();
   if (type == NotificationType::EXTENSION_LOADED) {
     AddExtension(extension);
   } else if (type == NotificationType::EXTENSION_UNLOADED ||
@@ -104,7 +104,7 @@ void ExtensionToolbarModel::Observe(NotificationType type,
   }
 }
 
-void ExtensionToolbarModel::AddExtension(Extension* extension) {
+void ExtensionToolbarModel::AddExtension(const Extension* extension) {
   // We only care about extensions with browser actions.
   if (!extension->browser_action())
     return;
@@ -126,7 +126,7 @@ void ExtensionToolbarModel::AddExtension(Extension* extension) {
   UpdatePrefs();
 }
 
-void ExtensionToolbarModel::RemoveExtension(Extension* extension) {
+void ExtensionToolbarModel::RemoveExtension(const Extension* extension) {
   ExtensionList::iterator pos = std::find(begin(), end(), extension);
   if (pos == end()) {
     return;
@@ -162,7 +162,7 @@ void ExtensionToolbarModel::InitializeExtensionList() {
 
   // Create the lists.
   for (size_t i = 0; i < service_->extensions()->size(); ++i) {
-    Extension* extension = service_->extensions()->at(i);
+    const Extension* extension = service_->extensions()->at(i);
     if (!extension->browser_action())
       continue;
 
@@ -208,7 +208,7 @@ void ExtensionToolbarModel::UpdatePrefs() {
   service_->extension_prefs()->SetToolbarOrder(ids);
 }
 
-Extension* ExtensionToolbarModel::GetExtensionByIndex(int index) const {
+const Extension* ExtensionToolbarModel::GetExtensionByIndex(int index) const {
   return toolitems_.at(index);
 }
 
diff --git a/chrome/browser/extensions/extension_toolbar_model.h b/chrome/browser/extensions/extension_toolbar_model.h
index a38fc8c..37c3a08 100644
--- a/chrome/browser/extensions/extension_toolbar_model.h
+++ b/chrome/browser/extensions/extension_toolbar_model.h
@@ -30,13 +30,13 @@ class ExtensionToolbarModel : public NotificationObserver {
    public:
     // An extension with a browser action button has been added, and should go
     // in the toolbar at |index|.
-    virtual void BrowserActionAdded(Extension* extension, int index) {}
+    virtual void BrowserActionAdded(const Extension* extension, int index) {}
 
     // The browser action button for |extension| should no longer show.
-    virtual void BrowserActionRemoved(Extension* extension) {}
+    virtual void BrowserActionRemoved(const Extension* extension) {}
 
     // The browser action button for |extension| has been moved to |index|.
-    virtual void BrowserActionMoved(Extension* extension, int index) {}
+    virtual void BrowserActionMoved(const Extension* extension, int index) {}
 
     // Called when the model has finished loading.
     virtual void ModelLoaded() {}
@@ -48,7 +48,7 @@ class ExtensionToolbarModel : public NotificationObserver {
   // Functions called by the view.
   void AddObserver(Observer* observer);
   void RemoveObserver(Observer* observer);
-  void MoveBrowserAction(Extension* extension, int index);
+  void MoveBrowserAction(const Extension* extension, int index);
   // If count == size(), this will set the visible icon count to -1, meaning
   // "show all actions".
   void SetVisibleIconCount(int count);
@@ -69,7 +69,7 @@ class ExtensionToolbarModel : public NotificationObserver {
     return toolitems_.end();
   }
 
-  Extension* GetExtensionByIndex(int index) const;
+  const 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.
@@ -93,8 +93,8 @@ class ExtensionToolbarModel : public NotificationObserver {
   // Our observers.
   ObserverList<Observer> observers_;
 
-  void AddExtension(Extension* extension);
-  void RemoveExtension(Extension* extension);
+  void AddExtension(const Extension* extension);
+  void RemoveExtension(const Extension* extension);
 
   // Our ExtensionsService, guaranteed to outlive us.
   ExtensionsService* service_;
diff --git a/chrome/browser/extensions/extension_toolbar_model_browsertest.cc b/chrome/browser/extensions/extension_toolbar_model_browsertest.cc
index 031672e..45c936e 100644
--- a/chrome/browser/extensions/extension_toolbar_model_browsertest.cc
+++ b/chrome/browser/extensions/extension_toolbar_model_browsertest.cc
@@ -37,19 +37,19 @@ class ExtensionToolbarModelTest : public ExtensionBrowserTest,
     model_->RemoveObserver(this);
   }
 
-  virtual void BrowserActionAdded(Extension* extension, int index) {
+  virtual void BrowserActionAdded(const Extension* extension, int index) {
     inserted_count_++;
   }
 
-  virtual void BrowserActionRemoved(Extension* extension) {
+  virtual void BrowserActionRemoved(const Extension* extension) {
     removed_count_++;
   }
 
-  virtual void BrowserActionMoved(Extension* extension, int index) {
+  virtual void BrowserActionMoved(const Extension* extension, int index) {
     moved_count_++;
   }
 
-  Extension* ExtensionAt(int index) {
+  const Extension* ExtensionAt(int index) {
     for (ExtensionList::iterator i = model_->begin(); i < model_->end(); ++i) {
       if (index-- == 0)
         return *i;
@@ -87,7 +87,7 @@ IN_PROC_BROWSER_TEST_F(ExtensionToolbarModelTest, Basic) {
   // We should now find our extension in the model.
   EXPECT_EQ(1, inserted_count_);
   EXPECT_EQ(1u, model_->size());
-  Extension* extension = ExtensionAt(0);
+  const Extension* extension = ExtensionAt(0);
   ASSERT_TRUE(NULL != extension);
   EXPECT_STREQ("A browser action with no icon that makes the page red",
                extension->name().c_str());
@@ -96,7 +96,7 @@ IN_PROC_BROWSER_TEST_F(ExtensionToolbarModelTest, Basic) {
   model_->MoveBrowserAction(extension, 0);
   EXPECT_EQ(1, moved_count_);
   EXPECT_EQ(1u, model_->size());
-  Extension* extension2 = ExtensionAt(0);
+  const Extension* extension2 = ExtensionAt(0);
   EXPECT_EQ(extension, extension2);
 
   UnloadExtension(extension->id());
@@ -118,7 +118,7 @@ IN_PROC_BROWSER_TEST_F(ExtensionToolbarModelTest, ReorderAndReinsert) {
   // First extension loaded.
   EXPECT_EQ(1, inserted_count_);
   EXPECT_EQ(1u, model_->size());
-  Extension* extensionA = ExtensionAt(0);
+  const Extension* extensionA = ExtensionAt(0);
   ASSERT_TRUE(NULL != extensionA);
   EXPECT_STREQ("A browser action with no icon that makes the page red",
                extensionA->name().c_str());
@@ -132,7 +132,7 @@ IN_PROC_BROWSER_TEST_F(ExtensionToolbarModelTest, ReorderAndReinsert) {
   // Second extension loaded.
   EXPECT_EQ(2, inserted_count_);
   EXPECT_EQ(2u, model_->size());
-  Extension* extensionB = ExtensionAt(1);
+  const Extension* extensionB = ExtensionAt(1);
   ASSERT_TRUE(NULL != extensionB);
   EXPECT_STREQ("Popup tester", extensionB->name().c_str());
 
@@ -145,7 +145,7 @@ IN_PROC_BROWSER_TEST_F(ExtensionToolbarModelTest, ReorderAndReinsert) {
   // Third extension loaded.
   EXPECT_EQ(3, inserted_count_);
   EXPECT_EQ(3u, model_->size());
-  Extension* extensionC = ExtensionAt(2);
+  const Extension* extensionC = ExtensionAt(2);
   ASSERT_TRUE(NULL != extensionC);
   EXPECT_STREQ("A page action which removes a popup.",
                extensionC->name().c_str());
diff --git a/chrome/browser/extensions/extension_updater.cc b/chrome/browser/extensions/extension_updater.cc
index abdba15..df19489 100644
--- a/chrome/browser/extensions/extension_updater.cc
+++ b/chrome/browser/extensions/extension_updater.cc
@@ -734,7 +734,7 @@ bool ExtensionUpdater::GetExistingVersion(const std::string& id,
     *version = prefs_->GetString(kExtensionBlacklistUpdateVersion);
     return true;
   }
-  Extension* extension = service_->GetExtensionById(id, false);
+  const Extension* extension = service_->GetExtensionById(id, false);
   if (!extension) {
     return false;
   }
diff --git a/chrome/browser/extensions/extension_updater_unittest.cc b/chrome/browser/extensions/extension_updater_unittest.cc
index bae09c6..581be2b 100644
--- a/chrome/browser/extensions/extension_updater_unittest.cc
+++ b/chrome/browser/extensions/extension_updater_unittest.cc
@@ -57,7 +57,7 @@ class MockService : public ExtensionUpdateService {
     FAIL();
   }
 
-  virtual Extension* GetExtensionById(const std::string& id, bool) {
+  virtual const Extension* GetExtensionById(const std::string& id, bool) {
     ADD_FAILURE();
     return NULL;
   }
@@ -142,7 +142,7 @@ class ServiceForManifestTests : public MockService {
 
   virtual ~ServiceForManifestTests() {}
 
-  virtual Extension* GetExtensionById(const std::string& id, bool) {
+  virtual const Extension* GetExtensionById(const std::string& id, bool) {
     for (ExtensionList::iterator iter = extensions_.begin();
         iter != extensions_.end(); ++iter) {
      if ((*iter)->id() == id) {
@@ -194,7 +194,7 @@ class ServiceForDownloadTests : public MockService {
     return pending_extensions_;
   }
 
-  virtual Extension* GetExtensionById(const std::string& id, bool) {
+  virtual const Extension* GetExtensionById(const std::string& id, bool) {
     last_inquired_extension_id_ = id;
     return NULL;
   }
@@ -803,7 +803,7 @@ class ExtensionUpdaterTest : public testing::Test {
     service.set_extensions(tmp);
 
     ManifestFetchData fetch_data(update_url);
-    Extension* extension = tmp[0];
+    const Extension* extension = tmp[0];
     fetch_data.AddExtension(extension->id(), extension->VersionString(),
                             ManifestFetchData::kNeverPinged);
     UpdateManifest::Results results;
diff --git a/chrome/browser/extensions/extension_webstore_private_api.cc b/chrome/browser/extensions/extension_webstore_private_api.cc
index 3471cd4..5744beb 100644
--- a/chrome/browser/extensions/extension_webstore_private_api.cc
+++ b/chrome/browser/extensions/extension_webstore_private_api.cc
@@ -53,7 +53,7 @@ BrowserSignin* GetBrowserSignin(Profile* profile) {
 
 bool IsWebStoreURL(Profile* profile, const GURL& url) {
   ExtensionsService* service = profile->GetExtensionsService();
-  Extension* store = service->GetWebStoreApp();
+  const Extension* store = service->GetWebStoreApp();
   DCHECK(store);
   return (service->GetExtensionByWebExtent(url) == store);
 }
diff --git a/chrome/browser/extensions/extensions_service.cc b/chrome/browser/extensions/extensions_service.cc
index f48445e..5c81670 100644
--- a/chrome/browser/extensions/extensions_service.cc
+++ b/chrome/browser/extensions/extensions_service.cc
@@ -94,7 +94,7 @@ bool ShouldReloadExtensionManifest(const ExtensionInfo& info) {
   return extension_l10n_util::ShouldRelocalizeManifest(info);
 }
 
-void GetExplicitOriginsInExtent(Extension* extension,
+void GetExplicitOriginsInExtent(const Extension* extension,
                                 std::vector<GURL>* origins) {
   typedef std::vector<URLPattern> PatternList;
   std::set<GURL> set;
@@ -224,7 +224,7 @@ class ExtensionsServiceBackend
   // Note: We take ownership of |extension|.
   void OnExtensionUnpacked(const FilePath& crx_path,
                            const FilePath& unpacked_path,
-                           Extension* extension,
+                           const Extension* extension,
                            const std::string expected_id);
 
   // Notify the frontend that there was an error loading an extension.
@@ -295,7 +295,7 @@ void ExtensionsServiceBackend::LoadSingleExtension(
   file_util::AbsolutePath(&extension_path);
 
   std::string error;
-  scoped_refptr<Extension> extension = extension_file_util::LoadExtension(
+  scoped_refptr<const Extension> extension = extension_file_util::LoadExtension(
       extension_path,
       Extension::LOAD,
       false,  // Don't require id
@@ -439,7 +439,7 @@ void ExtensionsServiceBackend::ReloadExtensionManifests(
 
     // We need to reload original manifest in order to localize properly.
     std::string error;
-    scoped_refptr<Extension> extension(extension_file_util::LoadExtension(
+    scoped_refptr<const Extension> extension(extension_file_util::LoadExtension(
         info->extension_path, info->extension_location, false, &error));
 
     if (extension.get())
@@ -469,9 +469,9 @@ bool ExtensionsService::IsDownloadFromGallery(const GURL& download_url,
     return true;
   }
 
-  Extension* download_extension = GetExtensionByWebExtent(download_url);
-  Extension* referrer_extension = GetExtensionByWebExtent(referrer_url);
-  Extension* webstore_app = GetWebStoreApp();
+  const Extension* download_extension = GetExtensionByWebExtent(download_url);
+  const Extension* referrer_extension = GetExtensionByWebExtent(referrer_url);
+  const Extension* webstore_app = GetWebStoreApp();
 
   bool referrer_valid = (referrer_extension == webstore_app);
   bool download_valid = (download_extension == webstore_app);
@@ -762,7 +762,7 @@ void ExtensionsService::AddPendingExtensionInternal(
 void ExtensionsService::ReloadExtension(const std::string& extension_id) {
   DCHECK(BrowserThread::CurrentlyOn(BrowserThread::UI));
   FilePath path;
-  Extension* current_extension = GetExtensionById(extension_id, false);
+  const Extension* current_extension = GetExtensionById(extension_id, false);
 
   // Disable the extension if it's loaded. It might not be loaded if it crashed.
   if (current_extension) {
@@ -806,7 +806,8 @@ void ExtensionsService::UninstallExtension(const std::string& extension_id,
                                            bool external_uninstall) {
   DCHECK(BrowserThread::CurrentlyOn(BrowserThread::UI));
 
-  Extension* extension = GetExtensionByIdInternal(extension_id, true, true);
+  const Extension* extension =
+      GetExtensionByIdInternal(extension_id, true, true);
 
   // Callers should not send us nonexistent extensions.
   DCHECK(extension);
@@ -862,7 +863,8 @@ void ExtensionsService::ClearExtensionData(const GURL& extension_url) {
 void ExtensionsService::EnableExtension(const std::string& extension_id) {
   DCHECK(BrowserThread::CurrentlyOn(BrowserThread::UI));
 
-  Extension* extension = GetExtensionByIdInternal(extension_id, false, true);
+  const Extension* extension =
+      GetExtensionByIdInternal(extension_id, false, true);
   if (!extension) {
     return;
   }
@@ -886,7 +888,8 @@ void ExtensionsService::EnableExtension(const std::string& extension_id) {
 void ExtensionsService::DisableExtension(const std::string& extension_id) {
   DCHECK(BrowserThread::CurrentlyOn(BrowserThread::UI));
 
-  Extension* extension = GetExtensionByIdInternal(extension_id, true, false);
+  const Extension* extension =
+      GetExtensionByIdInternal(extension_id, true, false);
   // The extension may have been disabled already.
   if (!extension)
     return;
@@ -928,7 +931,7 @@ void ExtensionsService::LoadComponentExtensions() {
     }
 
     std::string error;
-    scoped_refptr<Extension> extension(Extension::Create(
+    scoped_refptr<const Extension> extension(Extension::Create(
         it->root_directory,
         Extension::COMPONENT,
         *static_cast<DictionaryValue*>(manifest.get()),
@@ -1068,7 +1071,7 @@ void ExtensionsService::ContinueLoadAllExtensions(
 void ExtensionsService::LoadInstalledExtension(const ExtensionInfo& info,
                                                bool write_to_prefs) {
   std::string error;
-  scoped_refptr<Extension> extension(NULL);
+  scoped_refptr<const Extension> extension(NULL);
   if (!extension_prefs_->IsExtensionAllowedByPolicy(info.extension_id)) {
     error = errors::kDisabledByPolicy;
   } else if (info.extension_manifest.get()) {
@@ -1104,7 +1107,7 @@ void ExtensionsService::LoadInstalledExtension(const ExtensionInfo& info,
   }
 }
 
-void ExtensionsService::NotifyExtensionLoaded(Extension* extension) {
+void ExtensionsService::NotifyExtensionLoaded(const Extension* extension) {
   // The ChromeURLRequestContexts need to be first to know that the extension
   // was loaded, otherwise a race can arise where a renderer that is created
   // for the extension may try to load an extension URL with an extension id
@@ -1127,14 +1130,14 @@ void ExtensionsService::NotifyExtensionLoaded(Extension* extension) {
   NotificationService::current()->Notify(
       NotificationType::EXTENSION_LOADED,
       Source<Profile>(profile_),
-      Details<Extension>(extension));
+      Details<const Extension>(extension));
 }
 
-void ExtensionsService::NotifyExtensionUnloaded(Extension* extension) {
+void ExtensionsService::NotifyExtensionUnloaded(const Extension* extension) {
   NotificationService::current()->Notify(
       NotificationType::EXTENSION_UNLOADED,
       Source<Profile>(profile_),
-      Details<Extension>(extension));
+      Details<const Extension>(extension));
 
   if (profile_) {
     profile_->UnregisterExtensionWithRequestContexts(extension);
@@ -1150,7 +1153,7 @@ void ExtensionsService::NotifyExtensionUnloaded(Extension* extension) {
   }
 }
 
-void ExtensionsService::GrantProtectedStorage(Extension* extension) {
+void ExtensionsService::GrantProtectedStorage(const Extension* extension) {
   DCHECK(extension->is_app()) << "Only Apps are allowed protected storage.";
   std::vector<GURL> origins;
   GetExplicitOriginsInExtent(extension, &origins);
@@ -1158,7 +1161,7 @@ void ExtensionsService::GrantProtectedStorage(Extension* extension) {
     ++protected_storage_map_[origins[i]];
 }
 
-void ExtensionsService::RevokeProtectedStorage(Extension* extension) {
+void ExtensionsService::RevokeProtectedStorage(const Extension* extension) {
   DCHECK(extension->is_app()) << "Attempting to revoke protected storage from "
       << " a non-app extension.";
   std::vector<GURL> origins;
@@ -1171,7 +1174,7 @@ void ExtensionsService::RevokeProtectedStorage(Extension* extension) {
   }
 }
 
-void ExtensionsService::GrantUnlimitedStorage(Extension* extension) {
+void ExtensionsService::GrantUnlimitedStorage(const Extension* extension) {
   DCHECK(extension->HasApiPermission(Extension::kUnlimitedStoragePermission));
   std::vector<GURL> origins;
   GetExplicitOriginsInExtent(extension, &origins);
@@ -1206,7 +1209,7 @@ void ExtensionsService::GrantUnlimitedStorage(Extension* extension) {
   }
 }
 
-void ExtensionsService::RevokeUnlimitedStorage(Extension* extension) {
+void ExtensionsService::RevokeUnlimitedStorage(const Extension* extension) {
   DCHECK(extension->HasApiPermission(Extension::kUnlimitedStoragePermission));
   std::vector<GURL> origins;
   GetExplicitOriginsInExtent(extension, &origins);
@@ -1255,7 +1258,7 @@ void ExtensionsService::UpdateExtensionBlacklist(
   // Loop current extensions, unload installed extensions.
   for (ExtensionList::const_iterator iter = extensions_.begin();
        iter != extensions_.end(); ++iter) {
-    Extension* extension = (*iter);
+    const Extension* extension = (*iter);
     if (blacklist_set.find(extension->id()) != blacklist_set.end()) {
       to_be_removed.push_back(extension->id());
     }
@@ -1279,7 +1282,7 @@ void ExtensionsService::CheckAdminBlacklist() {
   // Loop through extensions list, unload installed extensions.
   for (ExtensionList::const_iterator iter = extensions_.begin();
        iter != extensions_.end(); ++iter) {
-    Extension* extension = (*iter);
+    const Extension* extension = (*iter);
     if (!extension_prefs_->IsExtensionAllowedByPolicy(extension->id()))
       to_be_removed.push_back(extension->id());
   }
@@ -1300,7 +1303,7 @@ bool ExtensionsService::IsIncognitoEnabled(const Extension* extension) {
   return extension_prefs_->IsIncognitoEnabled(extension->id());
 }
 
-void ExtensionsService::SetIsIncognitoEnabled(Extension* extension,
+void ExtensionsService::SetIsIncognitoEnabled(const Extension* extension,
                                               bool enabled) {
   extension_prefs_->SetIsIncognitoEnabled(extension->id(), enabled);
 
@@ -1320,12 +1323,13 @@ bool ExtensionsService::AllowFileAccess(const Extension* extension) {
           extension_prefs_->AllowFileAccess(extension->id()));
 }
 
-void ExtensionsService::SetAllowFileAccess(Extension* extension, bool allow) {
+void ExtensionsService::SetAllowFileAccess(const Extension* extension,
+                                           bool allow) {
   extension_prefs_->SetAllowFileAccess(extension->id(), allow);
   NotificationService::current()->Notify(
       NotificationType::EXTENSION_USER_SCRIPTS_UPDATED,
       Source<Profile>(profile_),
-      Details<Extension>(extension));
+      Details<const Extension>(extension));
 }
 
 void ExtensionsService::CheckForExternalUpdates() {
@@ -1343,7 +1347,7 @@ void ExtensionsService::CheckForExternalUpdates() {
 
 void ExtensionsService::UnloadExtension(const std::string& extension_id) {
   // Make sure the extension gets deleted after we return from this function.
-  scoped_refptr<Extension> extension(
+  scoped_refptr<const Extension> extension(
       GetExtensionByIdInternal(extension_id, true, true));
 
   // Callers should not send us nonexistent extensions.
@@ -1367,7 +1371,7 @@ void ExtensionsService::UnloadExtension(const std::string& extension_id) {
     NotificationService::current()->Notify(
         NotificationType::EXTENSION_UNLOADED_DISABLED,
         Source<Profile>(profile_),
-        Details<Extension>(extension.get()));
+        Details<const Extension>(extension.get()));
     return;
   }
 
@@ -1423,10 +1427,10 @@ void ExtensionsService::OnLoadedInstalledExtensions() {
       NotificationService::NoDetails());
 }
 
-void ExtensionsService::OnExtensionLoaded(Extension* extension,
+void ExtensionsService::OnExtensionLoaded(const Extension* extension,
                                           bool allow_privilege_increase) {
   // Ensure extension is deleted unless we transfer ownership.
-  scoped_refptr<Extension> scoped_extension(extension);
+  scoped_refptr<const Extension> scoped_extension(extension);
 
   // The extension is now loaded, remove its data from unloaded extension map.
   unloaded_extension_paths_.erase(extension->id());
@@ -1442,7 +1446,8 @@ void ExtensionsService::OnExtensionLoaded(Extension* extension,
       extension->location() == Extension::LOAD ||
       extension->location() == Extension::COMPONENT ||
       Extension::IsExternalLocation(extension->location())) {
-    Extension* old = GetExtensionByIdInternal(extension->id(), true, true);
+    const Extension* old = GetExtensionByIdInternal(extension->id(),
+                                                    true, true);
     if (old) {
       // CrxInstaller should have guaranteed that we aren't downgrading.
       CHECK(extension->version()->CompareTo(*(old->version())) >= 0);
@@ -1485,7 +1490,7 @@ void ExtensionsService::OnExtensionLoaded(Extension* extension,
         NotificationService::current()->Notify(
             NotificationType::EXTENSION_UPDATE_DISABLED,
             Source<Profile>(profile_),
-            Details<Extension>(extension));
+            Details<const Extension>(extension));
         break;
       default:
         NOTREACHED();
@@ -1518,12 +1523,12 @@ void ExtensionsService::UpdateActiveExtensionsInCrashReporter() {
   child_process_logging::SetActiveExtensions(extension_ids);
 }
 
-void ExtensionsService::OnExtensionInstalled(Extension* extension,
+void ExtensionsService::OnExtensionInstalled(const Extension* extension,
                                              bool allow_privilege_increase) {
   DCHECK(BrowserThread::CurrentlyOn(BrowserThread::UI));
 
   // Ensure extension is deleted unless we transfer ownership.
-  scoped_refptr<Extension> scoped_extension(extension);
+  scoped_refptr<const Extension> scoped_extension(extension);
   Extension::State initial_state = Extension::DISABLED;
   bool initial_enable_incognito = false;
   PendingExtensionMap::iterator it =
@@ -1645,12 +1650,12 @@ void ExtensionsService::OnExtensionInstalled(Extension* extension,
     NotificationService::current()->Notify(
         NotificationType::THEME_INSTALLED,
         Source<Profile>(profile_),
-        Details<Extension>(extension));
+        Details<const Extension>(extension));
   } else {
     NotificationService::current()->Notify(
         NotificationType::EXTENSION_INSTALLED,
         Source<Profile>(profile_),
-        Details<Extension>(extension));
+        Details<const Extension>(extension));
   }
 
   if (extension->is_app()) {
@@ -1663,9 +1668,8 @@ void ExtensionsService::OnExtensionInstalled(Extension* extension,
   OnExtensionLoaded(scoped_extension, allow_privilege_increase);
 }
 
-Extension* ExtensionsService::GetExtensionByIdInternal(const std::string& id,
-                                                       bool include_enabled,
-                                                       bool include_disabled) {
+const Extension* ExtensionsService::GetExtensionByIdInternal(
+    const std::string& id, bool include_enabled, bool include_disabled) {
   std::string lowercase_id = StringToLowerASCII(id);
   if (include_enabled) {
     for (ExtensionList::const_iterator iter = extensions_.begin();
@@ -1684,16 +1688,16 @@ Extension* ExtensionsService::GetExtensionByIdInternal(const std::string& id,
   return NULL;
 }
 
-Extension* ExtensionsService::GetWebStoreApp() {
+const Extension* ExtensionsService::GetWebStoreApp() {
   return GetExtensionById(extension_misc::kWebStoreAppId, false);
 }
 
-Extension* ExtensionsService::GetExtensionByURL(const GURL& url) {
+const Extension* ExtensionsService::GetExtensionByURL(const GURL& url) {
   return url.scheme() != chrome::kExtensionScheme ? NULL :
       GetExtensionById(url.host(), false);
 }
 
-Extension* ExtensionsService::GetExtensionByWebExtent(const GURL& url) {
+const Extension* ExtensionsService::GetExtensionByWebExtent(const GURL& url) {
   for (size_t i = 0; i < extensions_.size(); ++i) {
     if (extensions_[i]->web_extent().ContainsURL(url))
       return extensions_[i];
@@ -1707,11 +1711,11 @@ bool ExtensionsService::ExtensionBindingsAllowed(const GURL& url) {
     return true;
 
   // Allow bindings for all component, hosted apps.
-  Extension* extension = GetExtensionByWebExtent(url);
+  const Extension* extension = GetExtensionByWebExtent(url);
   return (extension && extension->location() == Extension::COMPONENT);
 }
 
-Extension* ExtensionsService::GetExtensionByOverlappingWebExtent(
+const Extension* ExtensionsService::GetExtensionByOverlappingWebExtent(
     const ExtensionExtent& extent) {
   for (size_t i = 0; i < extensions_.size(); ++i) {
     if (extensions_[i]->web_extent().OverlapsWith(extent))
@@ -1757,7 +1761,7 @@ void ExtensionsService::OnExternalExtensionFileFound(
   // Before even bothering to unpack, check and see if we already have this
   // version. This is important because these extensions are going to get
   // installed on every startup.
-  Extension* existing = GetExtensionById(id, true);
+  const Extension* existing = GetExtensionById(id, true);
   scoped_ptr<Version> other(Version::GetVersionFromString(version));
   if (existing) {
     switch (existing->version()->CompareTo(*other)) {
diff --git a/chrome/browser/extensions/extensions_service.h b/chrome/browser/extensions/extensions_service.h
index c00c264..213471c 100644
--- a/chrome/browser/extensions/extensions_service.h
+++ b/chrome/browser/extensions/extensions_service.h
@@ -89,8 +89,8 @@ class ExtensionUpdateService {
   virtual const PendingExtensionMap& pending_extensions() const = 0;
   virtual void UpdateExtension(const std::string& id, const FilePath& path,
                                const GURL& download_url) = 0;
-  virtual Extension* GetExtensionById(const std::string& id,
-                                      bool include_disabled) = 0;
+  virtual const Extension* GetExtensionById(const std::string& id,
+                                            bool include_disabled) = 0;
   virtual void UpdateExtensionBlacklist(
     const std::vector<std::string>& blacklist) = 0;
   virtual void CheckAdminBlacklist() = 0;
@@ -179,11 +179,11 @@ class ExtensionsService
 
   // Whether this extension can run in an incognito window.
   bool IsIncognitoEnabled(const Extension* extension);
-  void SetIsIncognitoEnabled(Extension* extension, bool enabled);
+  void SetIsIncognitoEnabled(const Extension* extension, bool enabled);
 
   // Whether this extension can inject scripts into pages with file URLs.
   bool AllowFileAccess(const Extension* extension);
-  void SetAllowFileAccess(Extension* extension, bool allow);
+  void SetAllowFileAccess(const Extension* extension, bool allow);
 
   // Initialize and start all installed extensions.
   void Init();
@@ -192,7 +192,8 @@ class ExtensionsService
   void InitEventRouters();
 
   // Look up an extension by ID.
-  Extension* GetExtensionById(const std::string& id, bool include_disabled) {
+  const Extension* GetExtensionById(const std::string& id,
+                                    bool include_disabled) {
     return GetExtensionByIdInternal(id, true, include_disabled);
   }
 
@@ -285,18 +286,19 @@ class ExtensionsService
   void GarbageCollectExtensions();
 
   // The App that represents the web store.
-  Extension* GetWebStoreApp();
+  const Extension* GetWebStoreApp();
 
   // Lookup an extension by |url|.
-  Extension* GetExtensionByURL(const GURL& url);
+  const Extension* GetExtensionByURL(const GURL& url);
 
   // If there is an extension for the specified url it is returned. Otherwise
   // returns the extension whose web extent contains |url|.
-  Extension* GetExtensionByWebExtent(const GURL& url);
+  const Extension* GetExtensionByWebExtent(const GURL& url);
 
   // Returns an extension that contains any URL that overlaps with the given
   // extent, if one exists.
-  Extension* GetExtensionByOverlappingWebExtent(const ExtensionExtent& extent);
+  const Extension* GetExtensionByOverlappingWebExtent(
+      const ExtensionExtent& extent);
 
   // Returns true if |url| should get extension api bindings and be permitted
   // to make api calls. Note that this is independent of what extension
@@ -321,11 +323,11 @@ class ExtensionsService
   virtual void OnLoadedInstalledExtensions();
 
   // Called when an extension has been loaded.
-  void OnExtensionLoaded(Extension* extension,
+  void OnExtensionLoaded(const Extension* extension,
                          bool allow_privilege_increase);
 
   // Called by the backend when an extension has been installed.
-  void OnExtensionInstalled(Extension* extension,
+  void OnExtensionInstalled(const Extension* extension,
                             bool allow_privilege_increase);
 
   // Called by the backend when an external extension is found.
@@ -411,9 +413,9 @@ class ExtensionsService
 
   // Look up an extension by ID, optionally including either or both of enabled
   // and disabled extensions.
-  Extension* GetExtensionByIdInternal(const std::string& id,
-                                      bool include_enabled,
-                                      bool include_disabled);
+  const Extension* GetExtensionByIdInternal(const std::string& id,
+                                            bool include_enabled,
+                                            bool include_disabled);
 
   // Like AddPendingExtension() but assumes an extension with the same
   // id is not already installed.
@@ -425,10 +427,10 @@ class ExtensionsService
       Extension::Location install_source);
 
   // Handles sending notification that |extension| was loaded.
-  void NotifyExtensionLoaded(Extension* extension);
+  void NotifyExtensionLoaded(const Extension* extension);
 
   // Handles sending notification that |extension| was unloaded.
-  void NotifyExtensionUnloaded(Extension* extension);
+  void NotifyExtensionUnloaded(const Extension* extension);
 
   // Helper that updates the active extension list used for crash reporting.
   void UpdateActiveExtensionsInCrashReporter();
@@ -437,10 +439,10 @@ class ExtensionsService
   void LoadInstalledExtension(const ExtensionInfo& info, bool write_to_prefs);
 
   // Helper methods to configure the storage services accordingly.
-  void GrantProtectedStorage(Extension* extension);
-  void RevokeProtectedStorage(Extension* extension);
-  void GrantUnlimitedStorage(Extension* extension);
-  void RevokeUnlimitedStorage(Extension* extension);
+  void GrantProtectedStorage(const Extension* extension);
+  void RevokeProtectedStorage(const Extension* extension);
+  void GrantUnlimitedStorage(const Extension* extension);
+  void RevokeUnlimitedStorage(const Extension* extension);
 
   // The profile this ExtensionsService is part of.
   Profile* profile_;
diff --git a/chrome/browser/extensions/extensions_service_unittest.cc b/chrome/browser/extensions/extensions_service_unittest.cc
index 18210a9..bcb3f86 100644
--- a/chrome/browser/extensions/extensions_service_unittest.cc
+++ b/chrome/browser/extensions/extensions_service_unittest.cc
@@ -421,7 +421,7 @@ class ExtensionsServiceTest
                        const NotificationDetails& details) {
     switch (type.value) {
       case NotificationType::EXTENSION_LOADED: {
-        Extension* extension = Details<Extension>(details).ptr();
+        const Extension* extension = Details<const Extension>(details).ptr();
         loaded_.push_back(extension);
         // The tests rely on the errors being in a certain order, which can vary
         // depending on how filesystem iteration works.
@@ -430,7 +430,7 @@ class ExtensionsServiceTest
       }
 
       case NotificationType::EXTENSION_UNLOADED: {
-        Extension* e = Details<Extension>(details).ptr();
+        const Extension* e = Details<const Extension>(details).ptr();
         unloaded_id_ = e->id();
         ExtensionList::iterator i =
             std::find(loaded_.begin(), loaded_.end(), e);
@@ -443,7 +443,7 @@ class ExtensionsServiceTest
       }
       case NotificationType::EXTENSION_INSTALLED:
       case NotificationType::THEME_INSTALLED:
-        installed_ = Details<Extension>(details).ptr();
+        installed_ = Details<const Extension>(details).ptr();
         break;
 
       default:
@@ -678,7 +678,7 @@ class ExtensionsServiceTest
  protected:
   ExtensionList loaded_;
   std::string unloaded_id_;
-  Extension* installed_;
+  const Extension* installed_;
 
  private:
   NotificationRegistrar registrar_;
@@ -776,7 +776,7 @@ TEST_F(ExtensionsServiceTest, LoadAllExtensionsFromDirectorySuccess) {
   ValidateIntegerPref(good2, "state", Extension::ENABLED);
   ValidateIntegerPref(good2, "location", Extension::INTERNAL);
 
-  Extension* extension = loaded_[0];
+  const Extension* extension = loaded_[0];
   const UserScriptList& scripts = extension->content_scripts();
   ASSERT_EQ(2u, scripts.size());
   EXPECT_EQ(3u, scripts[0].url_patterns().size());
@@ -1276,7 +1276,7 @@ TEST_F(ExtensionsServiceTest, InstallAppsWithUnlimtedStorage) {
   PackAndInstallExtension(extensions_path.AppendASCII("app1"), true);
   ValidatePrefKeyCount(++pref_count);
   ASSERT_EQ(1u, service_->extensions()->size());
-  Extension* extension = service_->extensions()->at(0);
+  const Extension* extension = service_->extensions()->at(0);
   const std::string id1 = extension->id();
   EXPECT_TRUE(extension->HasApiPermission(
                   Extension::kUnlimitedStoragePermission));
@@ -1334,7 +1334,7 @@ TEST_F(ExtensionsServiceTest, InstallAppsAndCheckStorageProtection) {
   PackAndInstallExtension(extensions_path.AppendASCII("app1"), true);
   ValidatePrefKeyCount(++pref_count);
   ASSERT_EQ(1u, service_->extensions()->size());
-  Extension* extension = service_->extensions()->at(0);
+  const Extension* extension = service_->extensions()->at(0);
   EXPECT_TRUE(extension->is_app());
   const std::string id1 = extension->id();
   EXPECT_FALSE(service_->protected_storage_map_.empty());
@@ -1463,7 +1463,7 @@ TEST_F(ExtensionsServiceTest, UpdateExtension) {
   FilePath path = extensions_path.AppendASCII("good.crx");
 
   InstallExtension(path, true);
-  Extension* good = service_->extensions()->at(0);
+  const Extension* good = service_->extensions()->at(0);
   ASSERT_EQ("1.0.0.0", good->VersionString());
   ASSERT_EQ(good_crx, good->id());
 
@@ -1498,7 +1498,7 @@ TEST_F(ExtensionsServiceTest, UpdateWillNotDowngrade) {
   FilePath path = extensions_path.AppendASCII("good2.crx");
 
   InstallExtension(path, true);
-  Extension* good = service_->extensions()->at(0);
+  const Extension* good = service_->extensions()->at(0);
   ASSERT_EQ("1.0.0.1", good->VersionString());
   ASSERT_EQ(good_crx, good->id());
 
@@ -1518,7 +1518,7 @@ TEST_F(ExtensionsServiceTest, UpdateToSameVersionIsNoop) {
   FilePath path = extensions_path.AppendASCII("good.crx");
 
   InstallExtension(path, true);
-  Extension* good = service_->extensions()->at(0);
+  const Extension* good = service_->extensions()->at(0);
   ASSERT_EQ(good_crx, good->id());
   UpdateExtension(good_crx, path, FAILED_SILENTLY);
 }
@@ -1533,7 +1533,7 @@ TEST_F(ExtensionsServiceTest, UpdateExtensionPreservesState) {
   FilePath path = extensions_path.AppendASCII("good.crx");
 
   InstallExtension(path, true);
-  Extension* good = service_->extensions()->at(0);
+  const Extension* good = service_->extensions()->at(0);
   ASSERT_EQ("1.0.0.0", good->VersionString());
   ASSERT_EQ(good_crx, good->id());
 
@@ -1545,7 +1545,7 @@ TEST_F(ExtensionsServiceTest, UpdateExtensionPreservesState) {
   path = extensions_path.AppendASCII("good2.crx");
   UpdateExtension(good_crx, path, INSTALLED);
   ASSERT_EQ(1u, service_->disabled_extensions()->size());
-  Extension* good2 = service_->disabled_extensions()->at(0);
+  const Extension* good2 = service_->disabled_extensions()->at(0);
   ASSERT_EQ("1.0.0.1", good2->version()->GetString());
   EXPECT_TRUE(service_->IsIncognitoEnabled(good2));
 }
@@ -1603,7 +1603,7 @@ TEST_F(ExtensionsServiceTest, UpdatePendingExtension) {
 
   EXPECT_FALSE(ContainsKey(service_->pending_extensions(), kGoodId));
 
-  Extension* extension = service_->GetExtensionById(kGoodId, true);
+  const Extension* extension = service_->GetExtensionById(kGoodId, true);
   ASSERT_TRUE(extension);
 
   bool enabled = service_->GetExtensionById(kGoodId, false);
@@ -1630,7 +1630,7 @@ TEST_F(ExtensionsServiceTest, UpdatePendingTheme) {
 
   EXPECT_FALSE(ContainsKey(service_->pending_extensions(), theme_crx));
 
-  Extension* extension = service_->GetExtensionById(theme_crx, true);
+  const Extension* extension = service_->GetExtensionById(theme_crx, true);
   ASSERT_TRUE(extension);
 
   EXPECT_EQ(Extension::ENABLED,
@@ -1655,7 +1655,7 @@ TEST_F(ExtensionsServiceTest, UpdatePendingExternalCrx) {
 
   EXPECT_FALSE(ContainsKey(service_->pending_extensions(), theme_crx));
 
-  Extension* extension = service_->GetExtensionById(theme_crx, true);
+  const Extension* extension = service_->GetExtensionById(theme_crx, true);
   ASSERT_TRUE(extension);
 
   EXPECT_EQ(Extension::ENABLED,
@@ -1682,7 +1682,7 @@ TEST_F(ExtensionsServiceTest, UpdatePendingCrxThemeMismatch) {
 
   EXPECT_FALSE(ContainsKey(service_->pending_extensions(), theme_crx));
 
-  Extension* extension = service_->GetExtensionById(theme_crx, true);
+  const Extension* extension = service_->GetExtensionById(theme_crx, true);
   ASSERT_FALSE(extension);
 }
 
@@ -1739,7 +1739,7 @@ TEST_F(ExtensionsServiceTest, UpdatePendingExtensionAlreadyInstalled) {
   FilePath path = extensions_path.AppendASCII("good.crx");
   InstallExtension(path, true);
   ASSERT_EQ(1u, service_->extensions()->size());
-  Extension* good = service_->extensions()->at(0);
+  const Extension* good = service_->extensions()->at(0);
 
   EXPECT_FALSE(good->is_theme());
 
@@ -1794,7 +1794,7 @@ TEST_F(ExtensionsServiceTest, UnloadBlacklistedExtension) {
   FilePath path = extensions_path.AppendASCII("good.crx");
 
   InstallExtension(path, true);
-  Extension* good = service_->extensions()->at(0);
+  const Extension* good = service_->extensions()->at(0);
   EXPECT_EQ(good_crx, good->id());
   UpdateExtension(good_crx, path, FAILED_SILENTLY);
 
@@ -2127,7 +2127,7 @@ TEST_F(ExtensionsServiceTest, ClearExtensionData) {
   path = path.AppendASCII("extensions");
   path = path.AppendASCII("good.crx");
   InstallExtension(path, true);
-  Extension* extension = service_->GetExtensionById(good_crx, false);
+  const Extension* extension = service_->GetExtensionById(good_crx, false);
   ASSERT_TRUE(extension);
   GURL ext_url(extension->url());
   string16 origin_id =
diff --git a/chrome/browser/extensions/extensions_ui.cc b/chrome/browser/extensions/extensions_ui.cc
index 45b1cb6..d3f6a6c 100644
--- a/chrome/browser/extensions/extensions_ui.cc
+++ b/chrome/browser/extensions/extensions_ui.cc
@@ -58,8 +58,7 @@
 
 namespace {
 
-bool ShouldShowExtension(Extension* extension) {
-
+bool ShouldShowExtension(const Extension* extension) {
   // Don't show themes since this page's UI isn't really useful for themes.
   if (extension->is_theme())
     return false;
@@ -407,7 +406,7 @@ void ExtensionsDOMHandler::OnIconsLoaded(DictionaryValue* json) {
 }
 
 ExtensionResource ExtensionsDOMHandler::PickExtensionIcon(
-    Extension* extension) {
+    const Extension* extension) {
   return extension->GetIconResource(Extension::EXTENSION_ICON_MEDIUM,
                                     ExtensionIconSet::MATCH_BIGGER);
 }
@@ -459,7 +458,7 @@ void ExtensionsDOMHandler::HandleEnableMessage(const ListValue* args) {
   if (enable_str == "true") {
     ExtensionPrefs* prefs = extensions_service_->extension_prefs();
     if (prefs->DidExtensionEscalatePermissions(extension_id)) {
-      Extension* extension =
+      const Extension* extension =
           extensions_service_->GetExtensionById(extension_id, true);
       ShowExtensionDisabledDialog(extensions_service_,
                                   dom_ui_->GetProfile(), extension);
@@ -476,8 +475,8 @@ void ExtensionsDOMHandler::HandleEnableIncognitoMessage(const ListValue* args) {
   std::string extension_id, enable_str;
   CHECK(args->GetString(0, &extension_id));
   CHECK(args->GetString(1, &enable_str));
-  Extension* extension = extensions_service_->GetExtensionById(extension_id,
-                                                               true);
+  const Extension* extension =
+      extensions_service_->GetExtensionById(extension_id, true);
   DCHECK(extension);
 
   // Flipping the incognito bit will generate unload/load notifications for the
@@ -501,15 +500,15 @@ void ExtensionsDOMHandler::HandleAllowFileAccessMessage(const ListValue* args) {
   std::string extension_id, allow_str;
   CHECK(args->GetString(0, &extension_id));
   CHECK(args->GetString(1, &allow_str));
-  Extension* extension = extensions_service_->GetExtensionById(extension_id,
-                                                               true);
+  const Extension* extension =
+      extensions_service_->GetExtensionById(extension_id, true);
   DCHECK(extension);
 
   extensions_service_->SetAllowFileAccess(extension, allow_str == "true");
 }
 
 void ExtensionsDOMHandler::HandleUninstallMessage(const ListValue* args) {
-  Extension* extension = GetExtension(args);
+  const Extension* extension = GetExtension(args);
   if (!extension)
     return;
 
@@ -527,7 +526,7 @@ void ExtensionsDOMHandler::InstallUIProceed() {
 
   // The extension can be uninstalled in another window while the UI was
   // showing. Do nothing in that case.
-  Extension* extension =
+  const Extension* extension =
       extensions_service_->GetExtensionById(extension_id_prompting_, true);
   if (!extension)
     return;
@@ -542,7 +541,7 @@ void ExtensionsDOMHandler::InstallUIAbort() {
 }
 
 void ExtensionsDOMHandler::HandleOptionsMessage(const ListValue* args) {
-  Extension* extension = GetExtension(args);
+  const Extension* extension = GetExtension(args);
   if (!extension || extension->options_url().is_empty())
     return;
   dom_ui_->GetProfile()->GetExtensionProcessManager()->OpenOptionsPage(
@@ -703,7 +702,7 @@ void ExtensionsDOMHandler::Observe(NotificationType type,
   }
 }
 
-Extension* ExtensionsDOMHandler::GetExtension(const ListValue* args) {
+const Extension* ExtensionsDOMHandler::GetExtension(const ListValue* args) {
   std::string extension_id = WideToASCII(ExtractStringValue(args));
   CHECK(!extension_id.empty());
   return extensions_service_->GetExtensionById(extension_id, true);
@@ -846,7 +845,7 @@ DictionaryValue* ExtensionsDOMHandler::CreateExtensionDetailValue(
 }
 
 std::vector<ExtensionPage> ExtensionsDOMHandler::GetActivePagesForExtension(
-    Extension* extension) {
+    const Extension* extension) {
   std::vector<ExtensionPage> result;
 
   // Get the extension process's active views.
@@ -872,7 +871,7 @@ std::vector<ExtensionPage> ExtensionsDOMHandler::GetActivePagesForExtension(
 
 void ExtensionsDOMHandler::GetActivePagesForExtensionProcess(
     RenderProcessHost* process,
-    Extension* extension,
+    const Extension* extension,
     std::vector<ExtensionPage> *result) {
   if (!process)
     return;
diff --git a/chrome/browser/extensions/extensions_ui.h b/chrome/browser/extensions/extensions_ui.h
index 5660eaa..c8c6143 100644
--- a/chrome/browser/extensions/extensions_ui.h
+++ b/chrome/browser/extensions/extensions_ui.h
@@ -178,7 +178,7 @@ class ExtensionsDOMHandler
   void HandleSelectFilePathMessage(const ListValue* args);
 
   // Utility for callbacks that get an extension ID as the sole argument.
-  Extension* GetExtension(const ListValue* args);
+  const Extension* GetExtension(const ListValue* args);
 
   // Forces a UI update if appropriate after a notification is received.
   void MaybeUpdateAfterNotification();
@@ -198,15 +198,16 @@ class ExtensionsDOMHandler
                        const NotificationDetails& details);
 
   // Helper that lists the current active html pages for an extension.
-  std::vector<ExtensionPage> GetActivePagesForExtension(Extension* extension);
+  std::vector<ExtensionPage> GetActivePagesForExtension(
+      const Extension* extension);
   void GetActivePagesForExtensionProcess(
       RenderProcessHost* process,
-      Extension* extension,
+      const Extension* extension,
       std::vector<ExtensionPage> *result);
 
   // Returns the best icon to display in the UI for an extension, or an empty
   // ExtensionResource if no good icon exists.
-  ExtensionResource PickExtensionIcon(Extension* extension);
+  ExtensionResource PickExtensionIcon(const Extension* extension);
 
   // Loads the extension resources into the json data, then calls OnIconsLoaded.
   // Takes ownership of |icons|.
diff --git a/chrome/browser/extensions/image_loading_tracker.cc b/chrome/browser/extensions/image_loading_tracker.cc
index f4f9bfd..496c3ad 100644
--- a/chrome/browser/extensions/image_loading_tracker.cc
+++ b/chrome/browser/extensions/image_loading_tracker.cc
@@ -134,7 +134,7 @@ ImageLoadingTracker::~ImageLoadingTracker() {
     loader_->StopTracking();
 }
 
-void ImageLoadingTracker::LoadImage(Extension* extension,
+void ImageLoadingTracker::LoadImage(const Extension* extension,
                                     const ExtensionResource& resource,
                                     const gfx::Size& max_size,
                                     CacheParam cache) {
@@ -187,7 +187,7 @@ void ImageLoadingTracker::Observe(NotificationType type,
   DCHECK(type == NotificationType::EXTENSION_UNLOADED ||
          type == NotificationType::EXTENSION_UNLOADED_DISABLED);
 
-  Extension* extension = Details<Extension>(details).ptr();
+  const Extension* extension = Details<const Extension>(details).ptr();
 
   // Remove all entries in the load_map_ referencing the extension. 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 bac2f04..0ce3703 100644
--- a/chrome/browser/extensions/image_loading_tracker.h
+++ b/chrome/browser/extensions/image_loading_tracker.h
@@ -64,13 +64,13 @@ class ImageLoadingTracker : public 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(Extension* extension,
+  void LoadImage(const Extension* extension,
                  const ExtensionResource& resource,
                  const gfx::Size& max_size,
                  CacheParam cache);
 
  private:
-  typedef std::map<int, Extension*> LoadMap;
+  typedef std::map<int, const Extension*> LoadMap;
 
   class ImageLoader;
 
diff --git a/chrome/browser/extensions/image_loading_tracker_unittest.cc b/chrome/browser/extensions/image_loading_tracker_unittest.cc
index d23e2f6..57b5268 100644
--- a/chrome/browser/extensions/image_loading_tracker_unittest.cc
+++ b/chrome/browser/extensions/image_loading_tracker_unittest.cc
@@ -163,7 +163,7 @@ TEST_F(ImageLoadingTrackerTest, DeleteExtensionWhileWaitingForCache) {
   NotificationService::current()->Notify(
       NotificationType::EXTENSION_UNLOADED,
       NotificationService::AllSources(),
-      Details<Extension>(extension.get()));
+      Details<const Extension>(extension.get()));
 
   // Chuck the extension, that way if anyone tries to access it we should crash
   // or get valgrind errors.
diff --git a/chrome/browser/extensions/page_action_apitest.cc b/chrome/browser/extensions/page_action_apitest.cc
index c03c030..95e029e 100644
--- a/chrome/browser/extensions/page_action_apitest.cc
+++ b/chrome/browser/extensions/page_action_apitest.cc
@@ -18,7 +18,7 @@
 IN_PROC_BROWSER_TEST_F(ExtensionApiTest, PageAction) {
   ASSERT_TRUE(test_server()->Start());
   ASSERT_TRUE(RunExtensionTest("page_action/basics")) << message_;
-  Extension* extension = GetSingleLoadedExtension();
+  const Extension* extension = GetSingleLoadedExtension();
   ASSERT_TRUE(extension) << message_;
   {
     // Tell the extension to update the page action state.
@@ -62,7 +62,7 @@ IN_PROC_BROWSER_TEST_F(ExtensionApiTest, PageAction) {
 IN_PROC_BROWSER_TEST_F(ExtensionApiTest, PageActionAddPopup) {
   // Load the extension, which has no default popup.
   ASSERT_TRUE(RunExtensionTest("page_action/add_popup")) << message_;
-  Extension* extension = GetSingleLoadedExtension();
+  const Extension* extension = GetSingleLoadedExtension();
   ASSERT_TRUE(extension) << message_;
 
   int tab_id = ExtensionTabUtil::GetTabId(browser()->GetSelectedTabContents());
@@ -107,7 +107,7 @@ IN_PROC_BROWSER_TEST_F(ExtensionApiTest, PageActionAddPopup) {
 IN_PROC_BROWSER_TEST_F(ExtensionApiTest, PageActionRemovePopup) {
   // Load the extension, which has a page action with a default popup.
   ASSERT_TRUE(RunExtensionTest("page_action/remove_popup")) << message_;
-  Extension* extension = GetSingleLoadedExtension();
+  const Extension* extension = GetSingleLoadedExtension();
   ASSERT_TRUE(extension) << message_;
 
   int tab_id = ExtensionTabUtil::GetTabId(browser()->GetSelectedTabContents());
@@ -136,7 +136,7 @@ IN_PROC_BROWSER_TEST_F(ExtensionApiTest, PageActionRemovePopup) {
 // break.
 IN_PROC_BROWSER_TEST_F(ExtensionApiTest, OldPageActions) {
   ASSERT_TRUE(RunExtensionTest("page_action/old_api")) << message_;
-  Extension* extension = GetSingleLoadedExtension();
+  const Extension* extension = GetSingleLoadedExtension();
   ASSERT_TRUE(extension) << message_;
 
   // Have the extension enable the page action.
@@ -161,7 +161,7 @@ IN_PROC_BROWSER_TEST_F(ExtensionApiTest, OldPageActions) {
 // Tests popups in page actions.
 IN_PROC_BROWSER_TEST_F(ExtensionApiTest, ShowPageActionPopup) {
   ASSERT_TRUE(RunExtensionTest("page_action/popup")) << message_;
-  Extension* extension = GetSingleLoadedExtension();
+  const Extension* extension = GetSingleLoadedExtension();
   ASSERT_TRUE(extension) << message_;
 
   ASSERT_TRUE(WaitForPageActionVisibilityChangeTo(1));
diff --git a/chrome/browser/extensions/sandboxed_extension_unpacker.h b/chrome/browser/extensions/sandboxed_extension_unpacker.h
index 383156b..8438482 100644
--- a/chrome/browser/extensions/sandboxed_extension_unpacker.h
+++ b/chrome/browser/extensions/sandboxed_extension_unpacker.h
@@ -29,7 +29,7 @@ class SandboxedExtensionUnpackerClient
   // for deleting this memory.
   virtual void OnUnpackSuccess(const FilePath& temp_dir,
                                const FilePath& extension_root,
-                               Extension* extension) = 0;
+                               const Extension* extension) = 0;
   virtual void OnUnpackFailure(const std::string& error) = 0;
 
  protected:
diff --git a/chrome/browser/extensions/sandboxed_extension_unpacker_unittest.cc b/chrome/browser/extensions/sandboxed_extension_unpacker_unittest.cc
index 0ba87d5..4d893e1 100644
--- a/chrome/browser/extensions/sandboxed_extension_unpacker_unittest.cc
+++ b/chrome/browser/extensions/sandboxed_extension_unpacker_unittest.cc
@@ -25,7 +25,7 @@ using testing::Invoke;
 
 void OnUnpackSuccess(const FilePath& temp_dir,
                      const FilePath& extension_root,
-                     Extension* extension) {
+                     const Extension* extension) {
   // Don't delete temp_dir here, we need to do some post op checking.
 }
 
@@ -37,7 +37,7 @@ class MockSandboxedExtensionUnpackerClient
   MOCK_METHOD3(OnUnpackSuccess,
                void(const FilePath& temp_dir,
                     const FilePath& extension_root,
-                    Extension* extension));
+                    const Extension* extension));
 
   MOCK_METHOD1(OnUnpackFailure,
                void(const std::string& error));
diff --git a/chrome/browser/extensions/theme_installed_infobar_delegate.cc b/chrome/browser/extensions/theme_installed_infobar_delegate.cc
index 6d00c22..ebfbe98 100644
--- a/chrome/browser/extensions/theme_installed_infobar_delegate.cc
+++ b/chrome/browser/extensions/theme_installed_infobar_delegate.cc
@@ -81,7 +81,7 @@ bool ThemeInstalledInfoBarDelegate::Cancel() {
   if (!previous_theme_id_.empty()) {
     ExtensionsService* service = profile_->GetExtensionsService();
     if (service) {
-      Extension* previous_theme =
+      const Extension* previous_theme =
           service->GetExtensionById(previous_theme_id_, true);
       if (previous_theme) {
         profile_->SetTheme(previous_theme);
@@ -102,7 +102,7 @@ void ThemeInstalledInfoBarDelegate::Observe(
     case NotificationType::BROWSER_THEME_CHANGED: {
       // If the new theme is different from what this info bar is associated
       // with, close this info bar since it is no longer relevant.
-      Extension* extension = Details<Extension>(details).ptr();
+      const Extension* extension = Details<const Extension>(details).ptr();
       if (!extension || theme_id_ != extension->id())
         tab_contents_->RemoveInfoBar(this);
       break;
@@ -113,6 +113,6 @@ void ThemeInstalledInfoBarDelegate::Observe(
   }
 }
 
-bool ThemeInstalledInfoBarDelegate::MatchesTheme(Extension* theme) {
+bool ThemeInstalledInfoBarDelegate::MatchesTheme(const Extension* theme) {
   return (theme && theme->id() == theme_id_);
 }
diff --git a/chrome/browser/extensions/theme_installed_infobar_delegate.h b/chrome/browser/extensions/theme_installed_infobar_delegate.h
index 2c54fa5..b1ed99e 100644
--- a/chrome/browser/extensions/theme_installed_infobar_delegate.h
+++ b/chrome/browser/extensions/theme_installed_infobar_delegate.h
@@ -33,7 +33,7 @@ class ThemeInstalledInfoBarDelegate : public ConfirmInfoBarDelegate,
 
   // Returns true if the given theme is the same as the one associated with this
   // info bar.
-  bool MatchesTheme(Extension* theme);
+  bool MatchesTheme(const Extension* theme);
 
   // NotificationObserver implementation.
   virtual void Observe(NotificationType type,
diff --git a/chrome/browser/extensions/user_script_listener.cc b/chrome/browser/extensions/user_script_listener.cc
index 4e84045..c553b1f 100644
--- a/chrome/browser/extensions/user_script_listener.cc
+++ b/chrome/browser/extensions/user_script_listener.cc
@@ -98,7 +98,7 @@ void UserScriptListener::ReplaceURLPatterns(const URLPatterns& patterns) {
   url_patterns_ = patterns;
 }
 
-void UserScriptListener::CollectURLPatterns(Extension* extension,
+void UserScriptListener::CollectURLPatterns(const Extension* extension,
                                             URLPatterns* patterns) {
   DCHECK(BrowserThread::CurrentlyOn(BrowserThread::UI));
 
@@ -118,12 +118,13 @@ void UserScriptListener::Observe(NotificationType type,
 
   switch (type.value) {
     case NotificationType::EXTENSION_LOADED: {
-      Extension* extension = Details<Extension>(details).ptr();
+      const Extension* extension = Details<const Extension>(details).ptr();
       if (extension->content_scripts().empty())
         return;  // no new patterns from this extension.
 
       URLPatterns new_patterns;
-      CollectURLPatterns(Details<Extension>(details).ptr(), &new_patterns);
+      CollectURLPatterns(Details<const Extension>(details).ptr(),
+                         &new_patterns);
       if (!new_patterns.empty()) {
         BrowserThread::PostTask(
             BrowserThread::IO, FROM_HERE,
@@ -134,7 +135,8 @@ void UserScriptListener::Observe(NotificationType type,
     }
 
     case NotificationType::EXTENSION_UNLOADED: {
-      Extension* unloaded_extension = Details<Extension>(details).ptr();
+      const Extension* unloaded_extension =
+          Details<const Extension>(details).ptr();
       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 05de21a..3ac83ed 100644
--- a/chrome/browser/extensions/user_script_listener.h
+++ b/chrome/browser/extensions/user_script_listener.h
@@ -82,7 +82,7 @@ class UserScriptListener
 
   // Helper to collect the extension's user script URL patterns in a list and
   // return it.
-  void CollectURLPatterns(Extension* extension, URLPatterns* patterns);
+  void CollectURLPatterns(const Extension* extension, URLPatterns* patterns);
 
   // NotificationObserver
   virtual void Observe(NotificationType type,
diff --git a/chrome/browser/extensions/user_script_master.cc b/chrome/browser/extensions/user_script_master.cc
index 55c6df2..1712bb6 100644
--- a/chrome/browser/extensions/user_script_master.cc
+++ b/chrome/browser/extensions/user_script_master.cc
@@ -339,7 +339,7 @@ void UserScriptMaster::Observe(NotificationType type,
       break;
     case NotificationType::EXTENSION_LOADED: {
       // Add any content scripts inside the extension.
-      Extension* extension = Details<Extension>(details).ptr();
+      const Extension* extension = Details<const Extension>(details).ptr();
       bool incognito_enabled = profile_->GetExtensionsService()->
           IsIncognitoEnabled(extension);
       bool allow_file_access = profile_->GetExtensionsService()->
@@ -357,7 +357,7 @@ void UserScriptMaster::Observe(NotificationType type,
     }
     case NotificationType::EXTENSION_UNLOADED: {
       // Remove any content scripts.
-      Extension* extension = Details<Extension>(details).ptr();
+      const Extension* extension = Details<const Extension>(details).ptr();
       UserScriptList new_lone_scripts;
       for (UserScriptList::iterator iter = lone_scripts_.begin();
            iter != lone_scripts_.end(); ++iter) {
@@ -373,7 +373,7 @@ void UserScriptMaster::Observe(NotificationType type,
       break;
     }
     case NotificationType::EXTENSION_USER_SCRIPTS_UPDATED: {
-      Extension* extension = Details<Extension>(details).ptr();
+      const Extension* extension = Details<const Extension>(details).ptr();
       UserScriptList new_lone_scripts;
       bool incognito_enabled = profile_->GetExtensionsService()->
           IsIncognitoEnabled(extension);
diff --git a/chrome/browser/geolocation/geolocation_permission_context.cc b/chrome/browser/geolocation/geolocation_permission_context.cc
index 7fb9aae..4d7c848 100644
--- a/chrome/browser/geolocation/geolocation_permission_context.cc
+++ b/chrome/browser/geolocation/geolocation_permission_context.cc
@@ -362,7 +362,7 @@ void GeolocationPermissionContext::RequestGeolocationPermission(
 
   ExtensionsService* extensions = profile_->GetExtensionsService();
   if (extensions) {
-    Extension* ext = extensions->GetExtensionByURL(requesting_frame);
+    const Extension* ext = extensions->GetExtensionByURL(requesting_frame);
     if (!ext)
       ext = extensions->GetExtensionByWebExtent(requesting_frame);
     if (ext && ext->HasApiPermission(Extension::kGeolocationPermission)) {
diff --git a/chrome/browser/gtk/browser_actions_toolbar_gtk.cc b/chrome/browser/gtk/browser_actions_toolbar_gtk.cc
index 53776cf..4ee92b1 100644
--- a/chrome/browser/gtk/browser_actions_toolbar_gtk.cc
+++ b/chrome/browser/gtk/browser_actions_toolbar_gtk.cc
@@ -83,7 +83,7 @@ class BrowserActionButton : public NotificationObserver,
                             public MenuGtk::Delegate {
  public:
   BrowserActionButton(BrowserActionsToolbarGtk* toolbar,
-                      Extension* extension,
+                      const Extension* extension,
                       GtkThemeProvider* theme_provider)
       : toolbar_(toolbar),
         extension_(extension),
@@ -143,7 +143,7 @@ class BrowserActionButton : public NotificationObserver,
 
   GtkWidget* widget() { return alignment_.get(); }
 
-  Extension* extension() { return extension_; }
+  const Extension* extension() { return extension_; }
 
   // NotificationObserver implementation.
   void Observe(NotificationType type,
@@ -312,7 +312,7 @@ class BrowserActionButton : public NotificationObserver,
   BrowserActionsToolbarGtk* toolbar_;
 
   // The extension that contains this browser action.
-  Extension* extension_;
+  const Extension* extension_;
 
   // The button for this browser action.
   scoped_ptr<CustomDrawButton> button_;
@@ -497,8 +497,8 @@ void BrowserActionsToolbarGtk::SetContainerWidth() {
     SetButtonHBoxWidth(WidthForIconCount(showing_actions));
 }
 
-void BrowserActionsToolbarGtk::CreateButtonForExtension(Extension* extension,
-                                                        int index) {
+void BrowserActionsToolbarGtk::CreateButtonForExtension(
+    const Extension* extension, int index) {
   if (!ShouldDisplayBrowserAction(extension))
     return;
 
@@ -535,7 +535,7 @@ void BrowserActionsToolbarGtk::CreateButtonForExtension(Extension* extension,
 }
 
 GtkWidget* BrowserActionsToolbarGtk::GetBrowserActionWidget(
-    Extension* extension) {
+    const Extension* extension) {
   ExtensionButtonMap::iterator it = extension_button_map_.find(
       extension->id());
   if (it == extension_button_map_.end())
@@ -544,7 +544,8 @@ GtkWidget* BrowserActionsToolbarGtk::GetBrowserActionWidget(
   return it->second.get()->widget();
 }
 
-void BrowserActionsToolbarGtk::RemoveButtonForExtension(Extension* extension) {
+void BrowserActionsToolbarGtk::RemoveButtonForExtension(
+    const Extension* extension) {
   if (extension_button_map_.erase(extension->id()))
     UpdateVisibility();
   UpdateChevronVisibility();
@@ -558,7 +559,7 @@ void BrowserActionsToolbarGtk::UpdateVisibility() {
 }
 
 bool BrowserActionsToolbarGtk::ShouldDisplayBrowserAction(
-    Extension* extension) {
+    const Extension* extension) {
   // Only display incognito-enabled extensions while in incognito mode.
   return (!profile_->IsOffTheRecord() ||
           profile_->GetExtensionsService()->IsIncognitoEnabled(extension));
@@ -577,7 +578,7 @@ void BrowserActionsToolbarGtk::AnimateToShowNIcons(int count) {
   resize_animation_.Show();
 }
 
-void BrowserActionsToolbarGtk::BrowserActionAdded(Extension* extension,
+void BrowserActionsToolbarGtk::BrowserActionAdded(const Extension* extension,
                                                   int index) {
   overflow_menu_.reset();
 
@@ -594,7 +595,8 @@ void BrowserActionsToolbarGtk::BrowserActionAdded(Extension* extension,
   }
 }
 
-void BrowserActionsToolbarGtk::BrowserActionRemoved(Extension* extension) {
+void BrowserActionsToolbarGtk::BrowserActionRemoved(
+    const Extension* extension) {
   overflow_menu_.reset();
 
   if (drag_button_ != NULL) {
@@ -610,7 +612,7 @@ void BrowserActionsToolbarGtk::BrowserActionRemoved(Extension* extension) {
   }
 }
 
-void BrowserActionsToolbarGtk::BrowserActionMoved(Extension* extension,
+void BrowserActionsToolbarGtk::BrowserActionMoved(const Extension* extension,
                                                   int index) {
   // We initiated this move action, and have already moved the button.
   if (drag_button_ != NULL)
@@ -648,7 +650,7 @@ void BrowserActionsToolbarGtk::AnimationEnded(const Animation* animation) {
 }
 
 void BrowserActionsToolbarGtk::ExecuteCommand(int command_id) {
-  Extension* extension = model_->GetExtensionByIndex(command_id);
+  const Extension* extension = model_->GetExtensionByIndex(command_id);
   ExtensionAction* browser_action = extension->browser_action();
 
   int tab_id = GetCurrentTabId();
@@ -870,7 +872,7 @@ gboolean BrowserActionsToolbarGtk::OnOverflowButtonPress(
     if (profile_->IsOffTheRecord())
       model_index = model_->IncognitoIndexToOriginal(i);
 
-    Extension* extension = model_->GetExtensionByIndex(model_index);
+    const Extension* extension = model_->GetExtensionByIndex(model_index);
     BrowserActionButton* button = extension_button_map_[extension->id()].get();
 
     overflow_menu_model_->AddItem(model_index, UTF8ToUTF16(extension->name()));
@@ -910,7 +912,7 @@ gboolean BrowserActionsToolbarGtk::OnOverflowMenuButtonPress(
   if (profile_->IsOffTheRecord())
     item_index = model_->IncognitoIndexToOriginal(item_index);
 
-  Extension* extension = model_->GetExtensionByIndex(item_index);
+  const Extension* extension = model_->GetExtensionByIndex(item_index);
   ExtensionButtonMap::iterator it = extension_button_map_.find(
       extension->id());
   if (it == extension_button_map_.end()) {
diff --git a/chrome/browser/gtk/browser_actions_toolbar_gtk.h b/chrome/browser/gtk/browser_actions_toolbar_gtk.h
index 455efee..72cf960 100644
--- a/chrome/browser/gtk/browser_actions_toolbar_gtk.h
+++ b/chrome/browser/gtk/browser_actions_toolbar_gtk.h
@@ -47,7 +47,7 @@ class BrowserActionsToolbarGtk : public ExtensionToolbarModel::Observer,
   // Returns the widget in use by the BrowserActionButton corresponding to
   // |extension|. Used in positioning the ExtensionInstalledBubble for
   // BrowserActions.
-  GtkWidget* GetBrowserActionWidget(Extension* extension);
+  GtkWidget* GetBrowserActionWidget(const Extension* extension);
 
   int button_count() { return extension_button_map_.size(); }
 
@@ -83,10 +83,10 @@ class BrowserActionsToolbarGtk : public ExtensionToolbarModel::Observer,
 
   // Create the UI for a single browser action. This will stick the button
   // at the end of the toolbar.
-  void CreateButtonForExtension(Extension* extension, int index);
+  void CreateButtonForExtension(const Extension* extension, int index);
 
   // Delete resources associated with UI for a browser action.
-  void RemoveButtonForExtension(Extension* extension);
+  void RemoveButtonForExtension(const Extension* extension);
 
   // Change the visibility of widget() based on whether we have any buttons
   // to show.
@@ -102,12 +102,12 @@ class BrowserActionsToolbarGtk : public ExtensionToolbarModel::Observer,
   // Returns true if this extension should be shown in this toolbar. This can
   // return false if we are in an incognito window and the extension is disabled
   // for incognito.
-  bool ShouldDisplayBrowserAction(Extension* extension);
+  bool ShouldDisplayBrowserAction(const Extension* extension);
 
   // ExtensionToolbarModel::Observer implementation.
-  virtual void BrowserActionAdded(Extension* extension, int index);
-  virtual void BrowserActionRemoved(Extension* extension);
-  virtual void BrowserActionMoved(Extension* extension, int index);
+  virtual void BrowserActionAdded(const Extension* extension, int index);
+  virtual void BrowserActionRemoved(const Extension* extension);
+  virtual void BrowserActionMoved(const Extension* extension, int index);
   virtual void ModelLoaded();
 
   // AnimationDelegate implementation.
diff --git a/chrome/browser/gtk/extension_infobar_gtk.cc b/chrome/browser/gtk/extension_infobar_gtk.cc
index b7355b1..35d86c0 100644
--- a/chrome/browser/gtk/extension_infobar_gtk.cc
+++ b/chrome/browser/gtk/extension_infobar_gtk.cc
@@ -47,7 +47,7 @@ void ExtensionInfoBarGtk::OnImageLoaded(
 
 void ExtensionInfoBarGtk::BuildWidgets() {
   // Start loading the image for the menu button.
-  Extension* extension = delegate_->extension_host()->extension();
+  const Extension* extension = delegate_->extension_host()->extension();
   ExtensionResource icon_resource = extension->GetIconResource(
       Extension::EXTENSION_ICON_BITTY, ExtensionIconSet::MATCH_EXACTLY);
   if (!icon_resource.relative_path().empty()) {
diff --git a/chrome/browser/gtk/extension_install_prompt2_gtk.cc b/chrome/browser/gtk/extension_install_prompt2_gtk.cc
index 9c66c20..cf78028 100644
--- a/chrome/browser/gtk/extension_install_prompt2_gtk.cc
+++ b/chrome/browser/gtk/extension_install_prompt2_gtk.cc
@@ -53,7 +53,7 @@ void OnDialogResponse(GtkDialog* dialog, int response_id,
 }
 
 void ShowInstallPromptDialog2(GtkWindow* parent, SkBitmap* skia_icon,
-                              Extension* extension,
+                              const Extension* extension,
                               ExtensionInstallUI::Delegate *delegate,
                               const std::vector<string16>& permissions) {
   // Build the dialog.
@@ -172,7 +172,10 @@ void ShowInstallPromptDialog2(GtkWindow* parent, SkBitmap* skia_icon,
 }  // namespace
 
 void ExtensionInstallUI::ShowExtensionInstallUIPrompt2Impl(
-    Profile* profile, Delegate* delegate, Extension* extension, SkBitmap* icon,
+    Profile* profile,
+    Delegate* delegate,
+    const Extension* extension,
+    SkBitmap* icon,
     const std::vector<string16>& permissions) {
   Browser* browser = BrowserList::GetLastActiveWithProfile(profile);
   if (!browser) {
diff --git a/chrome/browser/gtk/extension_install_prompt_gtk.cc b/chrome/browser/gtk/extension_install_prompt_gtk.cc
index bcb7c0a..a1166d0 100644
--- a/chrome/browser/gtk/extension_install_prompt_gtk.cc
+++ b/chrome/browser/gtk/extension_install_prompt_gtk.cc
@@ -38,7 +38,7 @@ void OnDialogResponse(GtkDialog* dialog, int response_id,
 }
 
 void ShowInstallPromptDialog(GtkWindow* parent, SkBitmap* skia_icon,
-                             Extension *extension,
+                             const Extension* extension,
                              ExtensionInstallUI::Delegate *delegate,
                              ExtensionInstallUI::PromptType type) {
   // Build the dialog.
@@ -87,7 +87,10 @@ void ShowInstallPromptDialog(GtkWindow* parent, SkBitmap* skia_icon,
 }  // namespace
 
 void ExtensionInstallUI::ShowExtensionInstallUIPromptImpl(
-    Profile* profile, Delegate* delegate, Extension* extension, SkBitmap* icon,
+    Profile* profile,
+    Delegate* delegate,
+    const Extension* extension,
+    SkBitmap* icon,
     ExtensionInstallUI::PromptType type) {
   Browser* browser = BrowserList::GetLastActiveWithProfile(profile);
   if (!browser) {
diff --git a/chrome/browser/gtk/extension_installed_bubble_gtk.cc b/chrome/browser/gtk/extension_installed_bubble_gtk.cc
index 0e54c14..af9c915 100644
--- a/chrome/browser/gtk/extension_installed_bubble_gtk.cc
+++ b/chrome/browser/gtk/extension_installed_bubble_gtk.cc
@@ -43,14 +43,14 @@ const int kContentBorder = 7;
 
 }  // namespace
 
-void ExtensionInstalledBubbleGtk::Show(Extension* extension, Browser* browser,
+void ExtensionInstalledBubbleGtk::Show(const Extension* extension,
+                                       Browser* browser,
                                        SkBitmap icon) {
   new ExtensionInstalledBubbleGtk(extension, browser, icon);
 }
 
-ExtensionInstalledBubbleGtk::ExtensionInstalledBubbleGtk(Extension *extension,
-                                                         Browser *browser,
-                                                         SkBitmap icon)
+ExtensionInstalledBubbleGtk::ExtensionInstalledBubbleGtk(
+    const Extension* extension, Browser *browser, SkBitmap icon)
     : extension_(extension),
       browser_(browser),
       icon_(icon),
@@ -83,7 +83,7 @@ void ExtensionInstalledBubbleGtk::Observe(NotificationType type,
                                           const NotificationSource& source,
                                           const NotificationDetails& details) {
   if (type == NotificationType::EXTENSION_LOADED) {
-    Extension* extension = Details<Extension>(details).ptr();
+    const Extension* extension = Details<const Extension>(details).ptr();
     if (extension == extension_) {
       // PostTask to ourself to allow all EXTENSION_LOADED Observers to run.
       MessageLoopForUI::current()->PostTask(FROM_HERE, NewRunnableMethod(this,
diff --git a/chrome/browser/gtk/extension_installed_bubble_gtk.h b/chrome/browser/gtk/extension_installed_bubble_gtk.h
index 9b8483c..08d6fec 100644
--- a/chrome/browser/gtk/extension_installed_bubble_gtk.h
+++ b/chrome/browser/gtk/extension_installed_bubble_gtk.h
@@ -45,13 +45,13 @@ class ExtensionInstalledBubbleGtk
   // the extension has loaded. |extension| is the installed extension. |browser|
   // is the browser window which will host the bubble. |icon| is the install
   // icon of the extension.
-  static void Show(Extension *extension, Browser *browser, SkBitmap icon);
+  static void Show(const Extension* extension, Browser *browser, SkBitmap icon);
 
  private:
   friend class base::RefCountedThreadSafe<ExtensionInstalledBubbleGtk>;
 
   // Private ctor. Registers a listener for EXTENSION_LOADED.
-  ExtensionInstalledBubbleGtk(Extension *extension, Browser *browser,
+  ExtensionInstalledBubbleGtk(const Extension* extension, Browser *browser,
                               SkBitmap icon);
 
   virtual ~ExtensionInstalledBubbleGtk();
@@ -74,7 +74,7 @@ class ExtensionInstalledBubbleGtk
   static void OnButtonClick(GtkWidget* button,
                             ExtensionInstalledBubbleGtk* toolbar);
 
-  Extension *extension_;
+  const Extension* extension_;
   Browser *browser_;
   SkBitmap icon_;
   NotificationRegistrar registrar_;
diff --git a/chrome/browser/gtk/gtk_theme_provider.cc b/chrome/browser/gtk/gtk_theme_provider.cc
index f33ccc2..6d04b57 100644
--- a/chrome/browser/gtk/gtk_theme_provider.cc
+++ b/chrome/browser/gtk/gtk_theme_provider.cc
@@ -319,7 +319,7 @@ void GtkThemeProvider::InitThemesFor(NotificationObserver* observer) {
                     NotificationService::NoDetails());
 }
 
-void GtkThemeProvider::SetTheme(Extension* extension) {
+void GtkThemeProvider::SetTheme(const Extension* extension) {
   profile()->GetPrefs()->SetBoolean(prefs::kUsesSystemTheme, false);
   LoadDefaultValues();
   BrowserThemeProvider::SetTheme(extension);
@@ -580,7 +580,7 @@ void GtkThemeProvider::LoadThemePrefs() {
   RebuildMenuIconSets();
 }
 
-void GtkThemeProvider::NotifyThemeChanged(Extension* extension) {
+void GtkThemeProvider::NotifyThemeChanged(const Extension* extension) {
   BrowserThemeProvider::NotifyThemeChanged(extension);
 
   // Notify all GtkChromeButtons of their new rendering mode:
diff --git a/chrome/browser/gtk/gtk_theme_provider.h b/chrome/browser/gtk/gtk_theme_provider.h
index 9a4d59c..f31d974 100644
--- a/chrome/browser/gtk/gtk_theme_provider.h
+++ b/chrome/browser/gtk/gtk_theme_provider.h
@@ -51,7 +51,7 @@ class GtkThemeProvider : public BrowserThemeProvider,
   virtual SkBitmap* GetBitmapNamed(int id) const;
   virtual SkColor GetColor(int id) const;
   virtual bool HasCustomImage(int id) const;
-  virtual void SetTheme(Extension* extension);
+  virtual void SetTheme(const Extension* extension);
   virtual void UseDefaultTheme();
   virtual void SetNativeTheme();
   virtual bool UsingDefaultTheme();
@@ -153,7 +153,7 @@ class GtkThemeProvider : public BrowserThemeProvider,
   virtual void LoadThemePrefs();
 
   // Let all the browser views know that themes have changed.
-  virtual void NotifyThemeChanged(Extension* extension);
+  virtual void NotifyThemeChanged(const Extension* extension);
 
   // Additionally frees the CairoCachedSurfaces.
   virtual void FreePlatformCaches();
diff --git a/chrome/browser/gtk/location_bar_view_gtk.cc b/chrome/browser/gtk/location_bar_view_gtk.cc
index c16b38c..1b5d398 100644
--- a/chrome/browser/gtk/location_bar_view_gtk.cc
+++ b/chrome/browser/gtk/location_bar_view_gtk.cc
@@ -1330,8 +1330,8 @@ LocationBarViewGtk::PageActionViewGtk::PageActionViewGtk(
   image_.Own(gtk_image_new());
   gtk_container_add(GTK_CONTAINER(event_box_.get()), image_.get());
 
-  Extension* extension = profile->GetExtensionsService()->GetExtensionById(
-      page_action->extension_id(), false);
+  const Extension* extension = profile->GetExtensionsService()->
+      GetExtensionById(page_action->extension_id(), false);
   DCHECK(extension);
 
   // Load all the icons declared in the manifest. This is the contents of the
@@ -1494,8 +1494,8 @@ gboolean LocationBarViewGtk::PageActionViewGtk::OnButtonPressed(
           event->button.button);
     }
   } else {
-    Extension* extension = profile_->GetExtensionsService()->GetExtensionById(
-        page_action()->extension_id(), false);
+    const Extension* extension = profile_->GetExtensionsService()->
+        GetExtensionById(page_action()->extension_id(), false);
 
     context_menu_model_ =
         new ExtensionContextMenuModel(extension, owner_->browser_, this);
diff --git a/chrome/browser/message_box_handler.cc b/chrome/browser/message_box_handler.cc
index c39d1b7..4150945 100644
--- a/chrome/browser/message_box_handler.cc
+++ b/chrome/browser/message_box_handler.cc
@@ -28,7 +28,8 @@ static std::wstring GetTitle(Profile* profile,
                              const GURL& frame_url) {
   ExtensionsService* extensions_service = profile->GetExtensionsService();
   if (extensions_service) {
-    Extension* extension = extensions_service->GetExtensionByURL(frame_url);
+    const Extension* extension =
+        extensions_service->GetExtensionByURL(frame_url);
     if (!extension)
       extension = extensions_service->GetExtensionByWebExtent(frame_url);
 
diff --git a/chrome/browser/notifications/desktop_notification_service.cc b/chrome/browser/notifications/desktop_notification_service.cc
index a4c45d5..e7530e4 100644
--- a/chrome/browser/notifications/desktop_notification_service.cc
+++ b/chrome/browser/notifications/desktop_notification_service.cc
@@ -600,7 +600,7 @@ string16 DesktopNotificationService::DisplayNameForOrigin(
   if (origin.SchemeIs(chrome::kExtensionScheme)) {
     ExtensionsService* ext_service = profile_->GetExtensionsService();
     if (ext_service) {
-      Extension* extension = ext_service->GetExtensionByURL(origin);
+      const Extension* extension = ext_service->GetExtensionByURL(origin);
       if (extension)
         return UTF8ToUTF16(extension->name());
     }
diff --git a/chrome/browser/notifications/notification_options_menu_model.cc b/chrome/browser/notifications/notification_options_menu_model.cc
index 60b41869..97d269c 100644
--- a/chrome/browser/notifications/notification_options_menu_model.cc
+++ b/chrome/browser/notifications/notification_options_menu_model.cc
@@ -68,7 +68,7 @@ string16 NotificationOptionsMenuModel::GetLabelForCommandId(int command_id)
     if (origin.SchemeIs(chrome::kExtensionScheme)) {
       ExtensionsService* ext_service =
           balloon_->profile()->GetExtensionsService();
-      Extension* extension = ext_service->GetExtensionByURL(origin);
+      const Extension* extension = ext_service->GetExtensionByURL(origin);
       if (extension) {
         ExtensionPrefs* extension_prefs = ext_service->extension_prefs();
         const std::string& id = extension->id();
@@ -126,7 +126,7 @@ void NotificationOptionsMenuModel::ExecuteCommand(int command_id) {
         service->GrantPermission(origin);
       break;
     case kToggleExtensionCommand: {
-      Extension* extension = ext_service->GetExtensionByURL(origin);
+      const Extension* extension = ext_service->GetExtensionByURL(origin);
       if (extension) {
         ExtensionPrefs* extension_prefs = ext_service->extension_prefs();
         const std::string& id = extension->id();
diff --git a/chrome/browser/plugin_service.cc b/chrome/browser/plugin_service.cc
index a3d636b..b8c54f3 100644
--- a/chrome/browser/plugin_service.cc
+++ b/chrome/browser/plugin_service.cc
@@ -364,7 +364,7 @@ void PluginService::Observe(NotificationType type,
                             const NotificationDetails& details) {
   switch (type.value) {
     case NotificationType::EXTENSION_LOADED: {
-      Extension* extension = Details<Extension>(details).ptr();
+      const Extension* extension = Details<const Extension>(details).ptr();
       bool plugins_changed = false;
       for (size_t i = 0; i < extension->plugins().size(); ++i) {
         const Extension::PluginInfo& plugin = extension->plugins()[i];
@@ -380,7 +380,7 @@ void PluginService::Observe(NotificationType type,
     }
 
     case NotificationType::EXTENSION_UNLOADED: {
-      Extension* extension = Details<Extension>(details).ptr();
+      const Extension* extension = Details<const Extension>(details).ptr();
       bool plugins_changed = false;
       for (size_t i = 0; i < extension->plugins().size(); ++i) {
         const Extension::PluginInfo& plugin = extension->plugins()[i];
diff --git a/chrome/browser/profile.cc b/chrome/browser/profile.cc
index 6c3a928..bd0c5c8 100644
--- a/chrome/browser/profile.cc
+++ b/chrome/browser/profile.cc
@@ -335,7 +335,7 @@ class OffTheRecordProfileImpl : public Profile,
     profile_->InitThemes();
   }
 
-  virtual void SetTheme(Extension* extension) {
+  virtual void SetTheme(const Extension* extension) {
     profile_->SetTheme(extension);
   }
 
@@ -347,7 +347,7 @@ class OffTheRecordProfileImpl : public Profile,
     profile_->ClearTheme();
   }
 
-  virtual Extension* GetTheme() {
+  virtual const Extension* GetTheme() {
     return profile_->GetTheme();
   }
 
diff --git a/chrome/browser/profile.h b/chrome/browser/profile.h
index 31b3fc8..fac699d 100644
--- a/chrome/browser/profile.h
+++ b/chrome/browser/profile.h
@@ -297,7 +297,7 @@ class Profile {
   virtual void InitThemes() = 0;
 
   // Set the theme to the specified extension.
-  virtual void SetTheme(Extension* extension) = 0;
+  virtual void SetTheme(const Extension* extension) = 0;
 
   // Set the theme to the machine's native theme.
   virtual void SetNativeTheme() = 0;
@@ -307,7 +307,7 @@ class Profile {
 
   // Gets the theme that was last set. Returns NULL if the theme is no longer
   // installed, if there is no installed theme, or the theme was cleared.
-  virtual Extension* GetTheme() = 0;
+  virtual const Extension* GetTheme() = 0;
 
   // Returns or creates the ThemeProvider associated with this profile
   virtual BrowserThemeProvider* GetThemeProvider() = 0;
@@ -330,12 +330,14 @@ class Profile {
   // notification has fired. The purpose for handling this event first is to
   // avoid race conditions by making sure URLRequestContexts learn about new
   // extensions before anything else needs them to know.
-  virtual void RegisterExtensionWithRequestContexts(Extension* extension) {}
+  virtual void RegisterExtensionWithRequestContexts(
+      const Extension* extension) {}
 
   // Called by the ExtensionsService that lives in this profile. Lets the
   // profile clean up its RequestContexts once all the listeners to the
   // EXTENSION_UNLOADED notification have finished running.
-  virtual void UnregisterExtensionWithRequestContexts(Extension* extension) {}
+  virtual void UnregisterExtensionWithRequestContexts(
+      const Extension* extension) {}
 
   // Returns the SSLConfigService for this profile.
   virtual net::SSLConfigService* GetSSLConfigService() = 0;
diff --git a/chrome/browser/profile_impl.cc b/chrome/browser/profile_impl.cc
index cce4096..c60c33b 100644
--- a/chrome/browser/profile_impl.cc
+++ b/chrome/browser/profile_impl.cc
@@ -774,7 +774,8 @@ URLRequestContextGetter* ProfileImpl::GetRequestContextForExtensions() {
   return extensions_request_context_;
 }
 
-void ProfileImpl::RegisterExtensionWithRequestContexts(Extension* extension) {
+void ProfileImpl::RegisterExtensionWithRequestContexts(
+    const Extension* extension) {
   // AddRef to ensure the data lives until the other thread gets it. Balanced in
   // OnNewExtensions.
   extension->static_data()->AddRef();
@@ -785,7 +786,8 @@ void ProfileImpl::RegisterExtensionWithRequestContexts(Extension* extension) {
                         extension->static_data()));
 }
 
-void ProfileImpl::UnregisterExtensionWithRequestContexts(Extension* extension) {
+void ProfileImpl::UnregisterExtensionWithRequestContexts(
+    const Extension* extension) {
   BrowserThread::PostTask(
       BrowserThread::IO, FROM_HERE,
       NewRunnableMethod(extension_info_map_.get(),
@@ -1033,7 +1035,7 @@ void ProfileImpl::InitThemes() {
   }
 }
 
-void ProfileImpl::SetTheme(Extension* extension) {
+void ProfileImpl::SetTheme(const Extension* extension) {
   InitThemes();
   theme_provider_.get()->SetTheme(extension);
 }
@@ -1048,7 +1050,7 @@ void ProfileImpl::ClearTheme() {
   theme_provider_.get()->UseDefaultTheme();
 }
 
-Extension* ProfileImpl::GetTheme() {
+const Extension* ProfileImpl::GetTheme() {
   InitThemes();
 
   std::string id = theme_provider_.get()->GetThemeID();
@@ -1220,7 +1222,7 @@ void ProfileImpl::Observe(NotificationType type,
               Source<Profile>(this), NotificationService::NoDetails());
     }
   } else if (NotificationType::THEME_INSTALLED == type) {
-    Extension* extension = Details<Extension>(details).ptr();
+    const Extension* extension = Details<const Extension>(details).ptr();
     SetTheme(extension);
   } else if (NotificationType::BOOKMARK_MODEL_LOADED == type) {
     GetProfileSyncService();  // Causes lazy-load if sync is enabled.
diff --git a/chrome/browser/profile_impl.h b/chrome/browser/profile_impl.h
index ac3f631..6bad987 100644
--- a/chrome/browser/profile_impl.h
+++ b/chrome/browser/profile_impl.h
@@ -72,17 +72,18 @@ class ProfileImpl : public Profile,
   virtual PersonalDataManager* GetPersonalDataManager();
   virtual FileSystemHostContext* GetFileSystemHostContext();
   virtual void InitThemes();
-  virtual void SetTheme(Extension* extension);
+  virtual void SetTheme(const Extension* extension);
   virtual void SetNativeTheme();
   virtual void ClearTheme();
-  virtual Extension* GetTheme();
+  virtual const Extension* GetTheme();
   virtual BrowserThemeProvider* GetThemeProvider();
   virtual bool HasCreatedDownloadManager() const;
   virtual URLRequestContextGetter* GetRequestContext();
   virtual URLRequestContextGetter* GetRequestContextForMedia();
   virtual URLRequestContextGetter* GetRequestContextForExtensions();
-  virtual void RegisterExtensionWithRequestContexts(Extension* extension);
-  virtual void UnregisterExtensionWithRequestContexts(Extension* extension);
+  virtual void RegisterExtensionWithRequestContexts(const Extension* extension);
+  virtual void UnregisterExtensionWithRequestContexts(
+      const Extension* extension);
   virtual net::SSLConfigService* GetSSLConfigService();
   virtual HostContentSettingsMap* GetHostContentSettingsMap();
   virtual HostZoomMap* GetHostZoomMap();
diff --git a/chrome/browser/renderer_host/browser_render_process_host.cc b/chrome/browser/renderer_host/browser_render_process_host.cc
index 9a4b0b7..e72c7b1 100644
--- a/chrome/browser/renderer_host/browser_render_process_host.cc
+++ b/chrome/browser/renderer_host/browser_render_process_host.cc
@@ -711,7 +711,7 @@ void BrowserRenderProcessHost::SendExtensionInfo() {
     return;
   ViewMsg_ExtensionsUpdated_Params params;
   for (size_t i = 0; i < service->extensions()->size(); ++i) {
-    Extension* extension = service->extensions()->at(i);
+    const Extension* extension = service->extensions()->at(i);
     ViewMsg_ExtensionRendererInfo info;
     info.id = extension->id();
     info.web_extent = extension->web_extent();
diff --git a/chrome/browser/renderer_host/site_instance.cc b/chrome/browser/renderer_host/site_instance.cc
index b0f4386..c6a660d 100644
--- a/chrome/browser/renderer_host/site_instance.cc
+++ b/chrome/browser/renderer_host/site_instance.cc
@@ -190,7 +190,7 @@ GURL SiteInstance::GetEffectiveURL(Profile* profile, const GURL& url) {
   if (!profile || !profile->GetExtensionsService())
     return url;
 
-  Extension* extension =
+  const Extension* extension =
       profile->GetExtensionsService()->GetExtensionByWebExtent(url);
   if (extension) {
     // If the URL is part of an extension's web extent, convert it to an
diff --git a/chrome/browser/search_engines/template_url_model.cc b/chrome/browser/search_engines/template_url_model.cc
index e7bcb92..5b5b02e 100644
--- a/chrome/browser/search_engines/template_url_model.cc
+++ b/chrome/browser/search_engines/template_url_model.cc
@@ -308,7 +308,7 @@ void TemplateURLModel::RemoveAutoGeneratedSince(Time created_after) {
   RemoveAutoGeneratedBetween(created_after, Time());
 }
 
-void TemplateURLModel::RegisterExtensionKeyword(Extension* extension) {
+void TemplateURLModel::RegisterExtensionKeyword(const Extension* extension) {
   // TODO(mpcomplete): disable the keyword when the extension is disabled.
   if (extension->omnibox_keyword().empty())
     return;
@@ -342,14 +342,14 @@ void TemplateURLModel::RegisterExtensionKeyword(Extension* extension) {
   NotifyObservers();
 }
 
-void TemplateURLModel::UnregisterExtensionKeyword(Extension* extension) {
+void TemplateURLModel::UnregisterExtensionKeyword(const Extension* extension) {
   const TemplateURL* url = GetTemplateURLForExtension(extension);
   if (url)
     Remove(url);
 }
 
 const TemplateURL* TemplateURLModel::GetTemplateURLForExtension(
-    Extension* extension) const {
+    const Extension* extension) const {
   for (TemplateURLVector::const_iterator i = template_urls_.begin();
        i != template_urls_.end(); ++i) {
     if ((*i)->IsExtensionKeyword() && (*i)->url()->GetHost() == extension->id())
@@ -741,7 +741,7 @@ void TemplateURLModel::NotifyLoaded() {
       NotificationService::NoDetails());
 
   for (size_t i = 0; i < pending_extension_ids_.size(); ++i) {
-    Extension* extension = profile_->GetExtensionsService()->
+    const Extension* extension = profile_->GetExtensionsService()->
         GetExtensionById(pending_extension_ids_[i], true);
     if (extension)
       RegisterExtensionKeyword(extension);
diff --git a/chrome/browser/search_engines/template_url_model.h b/chrome/browser/search_engines/template_url_model.h
index ce9a874..a16bad7 100644
--- a/chrome/browser/search_engines/template_url_model.h
+++ b/chrome/browser/search_engines/template_url_model.h
@@ -144,16 +144,17 @@ class TemplateURLModel : public WebDataServiceConsumer,
   // If the given extension has an omnibox keyword, adds a TemplateURL for that
   // keyword. Only 1 keyword is allowed for a given extension. If the keyword
   // already exists for this extension, does nothing.
-  void RegisterExtensionKeyword(Extension* extension);
+  void RegisterExtensionKeyword(const Extension* extension);
 
   // Removes the TemplateURL containing the keyword for the given extension,
   // if any.
-  void UnregisterExtensionKeyword(Extension* extension);
+  void UnregisterExtensionKeyword(const Extension* extension);
 
   // Returns the TemplateURL associated with the keyword for this extension.
   // This works by checking the extension ID, not the keyword, so it will work
   // even if the user changed the keyword.
-  const TemplateURL* GetTemplateURLForExtension(Extension* extension) const;
+  const TemplateURL* GetTemplateURLForExtension(
+      const Extension* extension) const;
 
   // Returns the set of URLs describing the keywords. The elements are owned
   // by TemplateURLModel and should not be deleted.
diff --git a/chrome/browser/sessions/tab_restore_service.cc b/chrome/browser/sessions/tab_restore_service.cc
index 3d78771..c295d767 100644
--- a/chrome/browser/sessions/tab_restore_service.cc
+++ b/chrome/browser/sessions/tab_restore_service.cc
@@ -476,7 +476,7 @@ void TabRestoreService::PopulateTab(Tab* tab,
   if (tab->current_navigation_index == -1 && entry_count > 0)
     tab->current_navigation_index = 0;
 
-  Extension* extension = controller->tab_contents()->extension_app();
+  const Extension* extension = controller->tab_contents()->extension_app();
   if (extension)
     tab->extension_app_id = extension->id();
 
diff --git a/chrome/browser/sync/glue/extension_change_processor.cc b/chrome/browser/sync/glue/extension_change_processor.cc
index 0cc64a9..fcbbd01 100644
--- a/chrome/browser/sync/glue/extension_change_processor.cc
+++ b/chrome/browser/sync/glue/extension_change_processor.cc
@@ -71,7 +71,7 @@ void ExtensionChangeProcessor::Observe(NotificationType type,
       RemoveServerData(traits_, id, profile_->GetProfileSyncService());
     }
   } else {
-    const Extension* extension = Details<Extension>(details).ptr();
+    const Extension* extension = Details<const Extension>(details).ptr();
     CHECK(extension);
     VLOG(1) << "Updating server data for extension " << extension->id()
             << " (notification type = " << type.value << ")";
diff --git a/chrome/browser/sync/glue/extension_sync.cc b/chrome/browser/sync/glue/extension_sync.cc
index 51ccfd4..facf5f1 100644
--- a/chrome/browser/sync/glue/extension_sync.cc
+++ b/chrome/browser/sync/glue/extension_sync.cc
@@ -268,7 +268,7 @@ void TryUpdateClient(
       extension_data->merged_data();
   DcheckIsExtensionSpecificsValid(specifics);
   const std::string& id = specifics.id();
-  Extension* extension = extensions_service->GetExtensionById(id, true);
+  const Extension* extension = extensions_service->GetExtensionById(id, true);
   if (extension) {
     if (!IsExtensionValidAndSyncable(*extension, allowed_extension_types)) {
       LOG(DFATAL) << "TryUpdateClient() called for non-syncable extension "
@@ -446,7 +446,7 @@ void UpdateClient(const ExtensionSyncTraits& traits,
   DcheckIsExtensionSpecificsValid(server_data);
   ExtensionData extension_data =
       ExtensionData::FromData(ExtensionData::SERVER, server_data);
-  Extension* extension =
+  const Extension* extension =
       extensions_service->GetExtensionById(server_data.id(), true);
   if (extension) {
     if (!IsExtensionValidAndSyncable(
@@ -478,7 +478,7 @@ void UpdateClient(const ExtensionSyncTraits& traits,
 void RemoveFromClient(const ExtensionSyncTraits& traits,
                       const std::string& id,
                       ExtensionsService* extensions_service) {
-  Extension* extension = extensions_service->GetExtensionById(id, true);
+  const Extension* extension = extensions_service->GetExtensionById(id, true);
   if (extension) {
     if (IsExtensionValidAndSyncable(*extension,
                                     traits.allowed_extension_types)) {
diff --git a/chrome/browser/sync/glue/extension_util.cc b/chrome/browser/sync/glue/extension_util.cc
index a5d74d0..a0aa08e 100644
--- a/chrome/browser/sync/glue/extension_util.cc
+++ b/chrome/browser/sync/glue/extension_util.cc
@@ -232,7 +232,7 @@ bool IsExtensionOutdated(const Extension& extension,
 
 void SetExtensionProperties(
     const sync_pb::ExtensionSpecifics& specifics,
-    ExtensionsService* extensions_service, Extension* extension) {
+    ExtensionsService* extensions_service, const Extension* extension) {
   DcheckIsExtensionSpecificsValid(specifics);
   CHECK(extensions_service);
   CHECK(extension);
diff --git a/chrome/browser/sync/glue/extension_util.h b/chrome/browser/sync/glue/extension_util.h
index ca85e31..a46d1fb 100644
--- a/chrome/browser/sync/glue/extension_util.h
+++ b/chrome/browser/sync/glue/extension_util.h
@@ -132,7 +132,7 @@ bool IsExtensionOutdated(const Extension& extension,
 // valid.
 void SetExtensionProperties(
     const sync_pb::ExtensionSpecifics& specifics,
-    ExtensionsService* extensions_service, Extension* extension);
+    ExtensionsService* extensions_service, const Extension* extension);
 
 // Merge |specifics| into |merged_specifics|.  Both must be valid and
 // have the same ID.  The merge policy is currently to copy the
diff --git a/chrome/browser/sync/glue/theme_change_processor.cc b/chrome/browser/sync/glue/theme_change_processor.cc
index e22484c..55f9879 100644
--- a/chrome/browser/sync/glue/theme_change_processor.cc
+++ b/chrome/browser/sync/glue/theme_change_processor.cc
@@ -17,7 +17,7 @@
 namespace browser_sync {
 
 namespace {
-std::string GetThemeId(Extension* current_theme) {
+std::string GetThemeId(const Extension* current_theme) {
   if (current_theme) {
     DCHECK(current_theme->is_theme());
   }
@@ -39,10 +39,10 @@ void ThemeChangeProcessor::Observe(NotificationType type,
                                    const NotificationDetails& details) {
   DCHECK(running());
   DCHECK(profile_);
-  Extension* extension = Details<Extension>(details).ptr();
+  const Extension* extension = Details<const Extension>(details).ptr();
   std::string current_or_future_theme_id =
       profile_->GetThemeProvider()->GetThemeID();
-  Extension* current_theme = profile_->GetTheme();
+  const Extension* current_theme = profile_->GetTheme();
   switch (type.value) {
     case NotificationType::BROWSER_THEME_CHANGED:
       // We pay attention to this notification only when it signifies
diff --git a/chrome/browser/sync/glue/theme_util.cc b/chrome/browser/sync/glue/theme_util.cc
index f8b72d1..0f2a16b 100644
--- a/chrome/browser/sync/glue/theme_util.cc
+++ b/chrome/browser/sync/glue/theme_util.cc
@@ -87,7 +87,7 @@ void SetCurrentThemeFromThemeSpecifics(
     VLOG(1) << "Applying theme " << id << " with update_url " << update_url;
     ExtensionsService* extensions_service = profile->GetExtensionsService();
     CHECK(extensions_service);
-    Extension* extension = extensions_service->GetExtensionById(id, true);
+    const Extension* extension = extensions_service->GetExtensionById(id, true);
     if (extension) {
       if (!extension->is_theme()) {
         VLOG(1) << "Extension " << id << " is not a theme; aborting";
diff --git a/chrome/browser/tab_contents/render_view_context_menu.cc b/chrome/browser/tab_contents/render_view_context_menu.cc
index 2d85f69..afd5ccb 100644
--- a/chrome/browser/tab_contents/render_view_context_menu.cc
+++ b/chrome/browser/tab_contents/render_view_context_menu.cc
@@ -180,7 +180,7 @@ void RenderViewContextMenu::AppendExtensionItems(
     const std::string& extension_id, int* index) {
   ExtensionsService* service = profile_->GetExtensionsService();
   ExtensionMenuManager* manager = service->menu_manager();
-  Extension* extension = service->GetExtensionById(extension_id, false);
+  const Extension* extension = service->GetExtensionById(extension_id, false);
   DCHECK_GE(*index, 0);
   int max_index =
       IDC_EXTENSIONS_CONTEXT_CUSTOM_LAST - IDC_EXTENSIONS_CONTEXT_CUSTOM_FIRST;
@@ -318,7 +318,7 @@ void RenderViewContextMenu::AppendAllExtensionItems() {
   std::set<std::string> ids = menu_manager->ExtensionIds();
   std::vector<std::pair<std::string, std::string> > sorted_ids;
   for (std::set<std::string>::iterator i = ids.begin(); i != ids.end(); ++i) {
-    Extension* extension = service->GetExtensionById(*i, false);
+    const Extension* extension = service->GetExtensionById(*i, false);
     if (extension)
       sorted_ids.push_back(
           std::pair<std::string, std::string>(extension->name(), *i));
diff --git a/chrome/browser/tab_contents/render_view_host_delegate_helper.cc b/chrome/browser/tab_contents/render_view_host_delegate_helper.cc
index b94ab7d..68ca49b 100644
--- a/chrome/browser/tab_contents/render_view_host_delegate_helper.cc
+++ b/chrome/browser/tab_contents/render_view_host_delegate_helper.cc
@@ -45,7 +45,8 @@ RenderViewHostDelegateViewHelper::MaybeCreateBackgroundContents(
       !extensions_service->is_ready())
     return NULL;
 
-  Extension* extension = extensions_service->GetExtensionByURL(opener_url);
+  const Extension* extension =
+      extensions_service->GetExtensionByURL(opener_url);
   if (!extension)
     extension = extensions_service->GetExtensionByWebExtent(opener_url);
   if (!extension ||
diff --git a/chrome/browser/tab_contents/tab_contents.cc b/chrome/browser/tab_contents/tab_contents.cc
index 4e5e9b5..288b5b6 100644
--- a/chrome/browser/tab_contents/tab_contents.cc
+++ b/chrome/browser/tab_contents/tab_contents.cc
@@ -587,7 +587,7 @@ RenderProcessHost* TabContents::GetRenderProcessHost() const {
   return render_manager_.current_host()->process();
 }
 
-void TabContents::SetExtensionApp(Extension* extension) {
+void TabContents::SetExtensionApp(const Extension* extension) {
   DCHECK(!extension || extension->GetFullLaunchURL().is_valid());
   extension_app_ = extension;
 
@@ -605,7 +605,7 @@ void TabContents::SetExtensionAppById(const std::string& extension_app_id) {
 
   ExtensionsService* extension_service = profile()->GetExtensionsService();
   if (extension_service && extension_service->is_ready()) {
-    Extension* extension =
+    const Extension* extension =
         extension_service->GetExtensionById(extension_app_id, false);
     if (extension)
       SetExtensionApp(extension);
@@ -3157,7 +3157,7 @@ void TabContents::Observe(NotificationType type,
   }
 }
 
-void TabContents::UpdateExtensionAppIcon(Extension* extension) {
+void TabContents::UpdateExtensionAppIcon(const Extension* extension) {
   extension_app_icon_.reset();
 
   if (extension) {
@@ -3174,12 +3174,12 @@ void TabContents::UpdateExtensionAppIcon(Extension* extension) {
   }
 }
 
-Extension* TabContents::GetExtensionContaining(const GURL& url) {
+const Extension* TabContents::GetExtensionContaining(const GURL& url) {
   ExtensionsService* extensions_service = profile()->GetExtensionsService();
   if (!extensions_service)
     return NULL;
 
-  Extension* extension = extensions_service->GetExtensionByURL(url);
+  const Extension* extension = extensions_service->GetExtensionByURL(url);
   return extension ?
       extension : extensions_service->GetExtensionByWebExtent(url);
 }
diff --git a/chrome/browser/tab_contents/tab_contents.h b/chrome/browser/tab_contents/tab_contents.h
index e6a834c..bfe9c55 100644
--- a/chrome/browser/tab_contents/tab_contents.h
+++ b/chrome/browser/tab_contents/tab_contents.h
@@ -208,14 +208,14 @@ class TabContents : public PageNavigator,
   // 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(Extension* extension);
+  void SetExtensionApp(const 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
   // specified id.
   void SetExtensionAppById(const std::string& extension_app_id);
 
-  Extension* extension_app() const { return extension_app_; }
+  const Extension* extension_app() const { return extension_app_; }
   bool is_app() const { return extension_app_ != NULL; }
 
   // If an app extension has been explicitly set for this TabContents its icon
@@ -1050,11 +1050,11 @@ class TabContents : public PageNavigator,
   // App extensions related methods:
 
   // Returns the first extension whose extent contains |url|.
-  Extension* GetExtensionContaining(const GURL& url);
+  const Extension* GetExtensionContaining(const GURL& url);
 
   // Resets app_icon_ and if |extension| is non-null creates a new
   // ImageLoadingTracker to load the extension's image.
-  void UpdateExtensionAppIcon(Extension* extension);
+  void UpdateExtensionAppIcon(const Extension* extension);
 
   // ImageLoadingTracker::Observer.
   virtual void OnImageLoaded(SkBitmap* image, ExtensionResource resource,
@@ -1233,7 +1233,7 @@ class TabContents : public PageNavigator,
 
   // If non-null this tab is an app tab and this is the extension the tab was
   // created for.
-  Extension* extension_app_;
+  const Extension* extension_app_;
 
   // Icon for extension_app_ (if non-null) or extension_for_current_page_.
   SkBitmap extension_app_icon_;
diff --git a/chrome/browser/tabs/pinned_tab_codec.cc b/chrome/browser/tabs/pinned_tab_codec.cc
index 7b9e0b3..f6d2a08 100644
--- a/chrome/browser/tabs/pinned_tab_codec.cc
+++ b/chrome/browser/tabs/pinned_tab_codec.cc
@@ -43,7 +43,7 @@ static void EncodePinnedTab(TabStripModel* model,
 
   TabContents* tab_contents = model->GetTabContentsAt(index);
   if (model->IsAppTab(index)) {
-    Extension* extension = tab_contents->extension_app();
+    const Extension* extension = tab_contents->extension_app();
     DCHECK(extension);
     value->SetString(kAppID, extension->id());
     // For apps we use the launch url. We do this for the following reason:
diff --git a/chrome/browser/tabs/tab_strip_model.cc b/chrome/browser/tabs/tab_strip_model.cc
index 0d744e4..80f048b 100644
--- a/chrome/browser/tabs/tab_strip_model.cc
+++ b/chrome/browser/tabs/tab_strip_model.cc
@@ -756,7 +756,7 @@ void TabStripModel::Observe(NotificationType type,
     }
 
     case NotificationType::EXTENSION_UNLOADED: {
-      Extension* extension = Details<Extension>(details).ptr();
+      const Extension* extension = Details<const Extension>(details).ptr();
       // Iterate backwards as we may remove items while iterating.
       for (int i = count() - 1; i >= 0; i--) {
         TabContents* contents = GetTabContentsAt(i);
diff --git a/chrome/browser/themes/browser_theme_pack.cc b/chrome/browser/themes/browser_theme_pack.cc
index cd7c2f9..56cbdbf 100644
--- a/chrome/browser/themes/browser_theme_pack.cc
+++ b/chrome/browser/themes/browser_theme_pack.cc
@@ -326,7 +326,8 @@ BrowserThemePack::~BrowserThemePack() {
 }
 
 // static
-BrowserThemePack* BrowserThemePack::BuildFromExtension(Extension* extension) {
+BrowserThemePack* BrowserThemePack::BuildFromExtension(
+    const Extension* extension) {
   DCHECK(BrowserThread::CurrentlyOn(BrowserThread::UI));
   DCHECK(extension);
   DCHECK(extension->is_theme());
@@ -576,7 +577,7 @@ BrowserThemePack::BrowserThemePack()
       source_images_(NULL) {
 }
 
-void BrowserThemePack::BuildHeader(Extension* extension) {
+void BrowserThemePack::BuildHeader(const Extension* extension) {
   header_ = new BrowserThemePackHeader;
   header_->version = kThemePackVersion;
 
diff --git a/chrome/browser/themes/browser_theme_pack.h b/chrome/browser/themes/browser_theme_pack.h
index 5fa55e2..d66b99b 100644
--- a/chrome/browser/themes/browser_theme_pack.h
+++ b/chrome/browser/themes/browser_theme_pack.h
@@ -46,7 +46,7 @@ class BrowserThemePack : public base::RefCountedThreadSafe<
   // Builds the theme pack from all data from |extension|. This is often done
   // on a separate thread as it takes so long. This can fail and return NULL in
   // the case where the theme has invalid data.
-  static BrowserThemePack* BuildFromExtension(Extension* extension);
+  static BrowserThemePack* BuildFromExtension(const Extension* extension);
 
   // Builds the theme pack from a previously performed WriteToDisk(). This
   // operation should be relatively fast, as it should be an mmap() and some
@@ -107,7 +107,7 @@ class BrowserThemePack : public base::RefCountedThreadSafe<
   virtual ~BrowserThemePack();
 
   // Builds a header ready to write to disk.
-  void BuildHeader(Extension* extension);
+  void BuildHeader(const Extension* extension);
 
   // Transforms the JSON tint values into their final versions in the |tints_|
   // array.
diff --git a/chrome/browser/themes/browser_theme_provider.cc b/chrome/browser/themes/browser_theme_provider.cc
index 58a6c31..134d954 100644
--- a/chrome/browser/themes/browser_theme_provider.cc
+++ b/chrome/browser/themes/browser_theme_provider.cc
@@ -288,7 +288,7 @@ RefCountedMemory* BrowserThemeProvider::GetRawData(int id) const {
   return data;
 }
 
-void BrowserThemeProvider::SetTheme(Extension* extension) {
+void BrowserThemeProvider::SetTheme(const Extension* extension) {
   // Clear our image cache.
   FreePlatformCaches();
 
@@ -557,7 +557,8 @@ void BrowserThemeProvider::LoadThemePrefs() {
       // theme is being migrated.
       ExtensionsService* service = profile_->GetExtensionsService();
       if (service) {
-        Extension* extension = service->GetExtensionById(current_id, false);
+        const Extension* extension =
+            service->GetExtensionById(current_id, false);
         if (extension) {
           DLOG(ERROR) << "Migrating theme";
           BuildFromExtension(extension);
@@ -573,13 +574,13 @@ void BrowserThemeProvider::LoadThemePrefs() {
   }
 }
 
-void BrowserThemeProvider::NotifyThemeChanged(Extension* extension) {
+void BrowserThemeProvider::NotifyThemeChanged(const Extension* extension) {
   VLOG(1) << "Sending BROWSER_THEME_CHANGED";
   // Redraw!
   NotificationService* service = NotificationService::current();
   service->Notify(NotificationType::BROWSER_THEME_CHANGED,
                   Source<BrowserThemeProvider>(this),
-                  Details<Extension>(extension));
+                  Details<const Extension>(extension));
 #if defined(OS_MACOSX)
   NotifyPlatformThemeChanged();
 #endif  // OS_MACOSX
@@ -600,7 +601,7 @@ void BrowserThemeProvider::SaveThemeID(const std::string& id) {
   profile_->GetPrefs()->SetString(prefs::kCurrentThemeID, id);
 }
 
-void BrowserThemeProvider::BuildFromExtension(Extension* extension) {
+void BrowserThemeProvider::BuildFromExtension(const Extension* extension) {
   scoped_refptr<BrowserThemePack> pack =
       BrowserThemePack::BuildFromExtension(extension);
   if (!pack.get()) {
diff --git a/chrome/browser/themes/browser_theme_provider.h b/chrome/browser/themes/browser_theme_provider.h
index f359072..a47f39c 100644
--- a/chrome/browser/themes/browser_theme_provider.h
+++ b/chrome/browser/themes/browser_theme_provider.h
@@ -152,7 +152,7 @@ class BrowserThemeProvider : public NonThreadSafe,
 #endif
 
   // Set the current theme to the theme defined in |extension|.
-  virtual void SetTheme(Extension* extension);
+  virtual void SetTheme(const Extension* extension);
 
   // Reset the theme to default.
   virtual void UseDefaultTheme();
@@ -221,7 +221,7 @@ class BrowserThemeProvider : public NonThreadSafe,
   // Let all the browser views know that themes have changed.
   // extension is NULL iff the theme is being set to the
   // default/system theme.
-  virtual void NotifyThemeChanged(Extension* extension);
+  virtual void NotifyThemeChanged(const Extension* extension);
 
 #if defined(OS_MACOSX)
   // Let all the browser views know that themes have changed in a platform way.
@@ -245,7 +245,7 @@ class BrowserThemeProvider : public NonThreadSafe,
 
   // Implementation of SetTheme() (and the fallback from LoadThemePrefs() in
   // case we don't have a theme pack).
-  void BuildFromExtension(Extension* extension);
+  void BuildFromExtension(const Extension* extension);
 
   // Remove preference values for themes that are no longer in use.
   void RemoveUnusedThemes();
diff --git a/chrome/browser/views/app_launched_animation_win.cc b/chrome/browser/views/app_launched_animation_win.cc
index 8a23d43..50efc5d 100644
--- a/chrome/browser/views/app_launched_animation_win.cc
+++ b/chrome/browser/views/app_launched_animation_win.cc
@@ -38,7 +38,7 @@ class AppLaunchedAnimationWin : public AnimationDelegate,
                                 public ImageLoadingTracker::Observer,
                                 public views::ImageView {
  public:
-  AppLaunchedAnimationWin(Extension* extension, const gfx::Rect& rect);
+  AppLaunchedAnimationWin(const Extension* extension, const gfx::Rect& rect);
 
  private:
   // AnimationDelegate
@@ -65,7 +65,7 @@ class AppLaunchedAnimationWin : public AnimationDelegate,
   DISALLOW_COPY_AND_ASSIGN(AppLaunchedAnimationWin);
 };
 
-AppLaunchedAnimationWin::AppLaunchedAnimationWin(Extension* extension,
+AppLaunchedAnimationWin::AppLaunchedAnimationWin(const Extension* extension,
                                                  const gfx::Rect& rect)
     : popup_(NULL),
       rect_(rect),
@@ -128,7 +128,8 @@ void AppLaunchedAnimationWin::OnImageLoaded(SkBitmap* image,
 }  // namespace
 
 // static
-void AppLaunchedAnimation::Show(Extension* extension, const gfx::Rect& rect) {
+void AppLaunchedAnimation::Show(const Extension* extension,
+                                const gfx::Rect& rect) {
   // The animation will delete itself when it's finished.
   new AppLaunchedAnimationWin(extension, rect);
 }
diff --git a/chrome/browser/views/browser_actions_container.cc b/chrome/browser/views/browser_actions_container.cc
index d2db56c..fb50270 100644
--- a/chrome/browser/views/browser_actions_container.cc
+++ b/chrome/browser/views/browser_actions_container.cc
@@ -58,7 +58,7 @@ bool BrowserActionsContainer::disable_animations_during_testing_ = false;
 ////////////////////////////////////////////////////////////////////////////////
 // BrowserActionButton
 
-BrowserActionButton::BrowserActionButton(Extension* extension,
+BrowserActionButton::BrowserActionButton(const Extension* extension,
                                          BrowserActionsContainer* panel)
     : ALLOW_THIS_IN_INITIALIZER_LIST(
           MenuButton(this, std::wstring(), NULL, false)),
@@ -281,7 +281,7 @@ BrowserActionButton::~BrowserActionButton() {
 ////////////////////////////////////////////////////////////////////////////////
 // BrowserActionView
 
-BrowserActionView::BrowserActionView(Extension* extension,
+BrowserActionView::BrowserActionView(const Extension* extension,
                                      BrowserActionsContainer* panel)
     : panel_(panel) {
   button_ = new BrowserActionButton(extension, panel);
@@ -838,7 +838,7 @@ void BrowserActionsContainer::MoveBrowserAction(const std::string& extension_id,
                                                 size_t new_index) {
   ExtensionsService* service = profile_->GetExtensionsService();
   if (service) {
-    Extension* extension = service->GetExtensionById(extension_id, false);
+    const Extension* extension = service->GetExtensionById(extension_id, false);
     model_->MoveBrowserAction(extension, new_index);
     SchedulePaint();
   }
@@ -886,7 +886,7 @@ int BrowserActionsContainer::IconHeight() {
   return icon_height;
 }
 
-void BrowserActionsContainer::BrowserActionAdded(Extension* extension,
+void BrowserActionsContainer::BrowserActionAdded(const Extension* extension,
                                                  int index) {
 #if defined(DEBUG)
   for (size_t i = 0; i < browser_action_views_.size(); ++i) {
@@ -924,7 +924,7 @@ void BrowserActionsContainer::BrowserActionAdded(Extension* extension,
   }
 }
 
-void BrowserActionsContainer::BrowserActionRemoved(Extension* extension) {
+void BrowserActionsContainer::BrowserActionRemoved(const Extension* extension) {
   CloseOverflowMenu();
 
   if (popup_ && popup_->host()->extension() == extension)
@@ -961,7 +961,7 @@ void BrowserActionsContainer::BrowserActionRemoved(Extension* extension) {
   }
 }
 
-void BrowserActionsContainer::BrowserActionMoved(Extension* extension,
+void BrowserActionsContainer::BrowserActionMoved(const Extension* extension,
                                                  int index) {
   if (!ShouldDisplayBrowserAction(extension))
     return;
@@ -1091,7 +1091,8 @@ void BrowserActionsContainer::SaveDesiredSizeAndAnimate(
   }
 }
 
-bool BrowserActionsContainer::ShouldDisplayBrowserAction(Extension* extension) {
+bool BrowserActionsContainer::ShouldDisplayBrowserAction(
+    const Extension* extension) {
   // Only display incognito-enabled extensions while in incognito mode.
   return (!profile_->IsOffTheRecord() ||
           profile_->GetExtensionsService()->IsIncognitoEnabled(extension));
diff --git a/chrome/browser/views/browser_actions_container.h b/chrome/browser/views/browser_actions_container.h
index cd376f7..0bc5fdd 100644
--- a/chrome/browser/views/browser_actions_container.h
+++ b/chrome/browser/views/browser_actions_container.h
@@ -54,13 +54,14 @@ class BrowserActionButton : public views::MenuButton,
                             public ImageLoadingTracker::Observer,
                             public NotificationObserver {
  public:
-  BrowserActionButton(Extension* extension, BrowserActionsContainer* panel);
+  BrowserActionButton(const Extension* extension,
+                      BrowserActionsContainer* panel);
 
   // Call this instead of delete.
   void Destroy();
 
   ExtensionAction* browser_action() const { return browser_action_; }
-  Extension* extension() { return extension_; }
+  const Extension* extension() { return extension_; }
 
   // Called to update the display to match the browser action's state.
   void UpdateState();
@@ -112,7 +113,7 @@ class BrowserActionButton : public views::MenuButton,
   ExtensionAction* browser_action_;
 
   // The extension associated with the browser action we're displaying.
-  Extension* extension_;
+  const Extension* extension_;
 
   // The object that is waiting for the image loading to complete
   // asynchronously.
@@ -146,7 +147,7 @@ class BrowserActionButton : public views::MenuButton,
 
 class BrowserActionView : public views::View {
  public:
-  BrowserActionView(Extension* extension, BrowserActionsContainer* panel);
+  BrowserActionView(const Extension* extension, BrowserActionsContainer* panel);
   virtual ~BrowserActionView();
 
   BrowserActionButton* button() { return button_; }
@@ -391,9 +392,9 @@ class BrowserActionsContainer
   static int IconHeight();
 
   // ExtensionToolbarModel::Observer implementation.
-  virtual void BrowserActionAdded(Extension* extension, int index);
-  virtual void BrowserActionRemoved(Extension* extension);
-  virtual void BrowserActionMoved(Extension* extension, int index);
+  virtual void BrowserActionAdded(const Extension* extension, int index);
+  virtual void BrowserActionRemoved(const Extension* extension);
+  virtual void BrowserActionMoved(const Extension* extension, int index);
   virtual void ModelLoaded();
 
   void LoadImages();
@@ -441,7 +442,7 @@ class BrowserActionsContainer
   // Returns true if this extension should be shown in this toolbar. This can
   // return false if we are in an incognito window and the extension is disabled
   // for incognito.
-  bool ShouldDisplayBrowserAction(Extension* extension);
+  bool ShouldDisplayBrowserAction(const Extension* extension);
 
   // The vector of browser actions (icons/image buttons for each action). Note
   // that not every BrowserAction in the ToolbarModel will necessarily be in
diff --git a/chrome/browser/views/browser_actions_container_browsertest.cc b/chrome/browser/views/browser_actions_container_browsertest.cc
index 664b510..ee30ddb 100644
--- a/chrome/browser/views/browser_actions_container_browsertest.cc
+++ b/chrome/browser/views/browser_actions_container_browsertest.cc
@@ -172,7 +172,7 @@ IN_PROC_BROWSER_TEST_F(BrowserActionsContainerTest, TestCrash57536) {
                                           .AppendASCII("browser_action")
                                           .AppendASCII("crash_57536")));
 
-  Extension* extension = service->extensions()->at(size_before);
+  const Extension* extension = service->extensions()->at(size_before);
 
   std::cout << "Creating bitmap\n" << std::flush;
 
diff --git a/chrome/browser/views/extensions/extension_install_prompt.cc b/chrome/browser/views/extensions/extension_install_prompt.cc
index 0aef60e..5cf1e7b 100644
--- a/chrome/browser/views/extensions/extension_install_prompt.cc
+++ b/chrome/browser/views/extensions/extension_install_prompt.cc
@@ -36,8 +36,10 @@ const int kIconSize = 69;
 class InstallDialogContent : public views::View, public views::DialogDelegate {
  public:
   InstallDialogContent(ExtensionInstallUI::Delegate* delegate,
-      Extension* extension, SkBitmap* icon, ExtensionInstallUI::PromptType type)
-          : delegate_(delegate), icon_(NULL), type_(type) {
+                       const Extension* extension,
+                       SkBitmap* icon,
+                       ExtensionInstallUI::PromptType type)
+        : delegate_(delegate), icon_(NULL), type_(type) {
     // Scale down to icon size, but allow smaller icons (don't scale up).
     gfx::Size size(icon->width(), icon->height());
     if (size.width() > kIconSize || size.height() > kIconSize)
@@ -142,7 +144,10 @@ class InstallDialogContent : public views::View, public views::DialogDelegate {
 
 // static
 void ExtensionInstallUI::ShowExtensionInstallUIPromptImpl(
-    Profile* profile, Delegate* delegate, Extension* extension, SkBitmap* icon,
+    Profile* profile,
+    Delegate* delegate,
+    const Extension* extension,
+    SkBitmap* icon,
     PromptType type) {
   Browser* browser = BrowserList::GetLastActiveWithProfile(profile);
   if (!browser) {
diff --git a/chrome/browser/views/extensions/extension_install_prompt2.cc b/chrome/browser/views/extensions/extension_install_prompt2.cc
index 467ae20..ba9631e 100644
--- a/chrome/browser/views/extensions/extension_install_prompt2.cc
+++ b/chrome/browser/views/extensions/extension_install_prompt2.cc
@@ -58,7 +58,7 @@ class InstallDialogContent2
     : public views::View, public views::DialogDelegate {
  public:
   InstallDialogContent2(ExtensionInstallUI::Delegate* delegate,
-                        Extension* extension,
+                        const Extension* extension,
                         SkBitmap* icon,
                         const std::vector<string16>& permissions);
 
@@ -109,7 +109,7 @@ class InstallDialogContent2
 
 
 InstallDialogContent2::InstallDialogContent2(
-    ExtensionInstallUI::Delegate* delegate, Extension* extension,
+    ExtensionInstallUI::Delegate* delegate, const Extension* extension,
     SkBitmap* icon, const std::vector<string16>& permissions)
         : delegate_(delegate),
           icon_(NULL),
@@ -292,7 +292,8 @@ void InstallDialogContent2::Layout() {
 
 // static
 void ExtensionInstallUI::ShowExtensionInstallUIPrompt2Impl(
-    Profile* profile, Delegate* delegate, Extension* extension, SkBitmap* icon,
+    Profile* profile, Delegate* delegate, const Extension* extension,
+    SkBitmap* icon,
     const std::vector<string16>& permissions) {
 #if defined(OS_CHROMEOS)
   // Use a normal browser window as parent on ChromeOS.
diff --git a/chrome/browser/views/extensions/extension_installed_bubble.cc b/chrome/browser/views/extensions/extension_installed_bubble.cc
index 27910e5..8cb9397 100644
--- a/chrome/browser/views/extensions/extension_installed_bubble.cc
+++ b/chrome/browser/views/extensions/extension_installed_bubble.cc
@@ -69,7 +69,7 @@ const int kAnimationWaitMaxRetry = 10;
 class InstalledBubbleContent : public views::View,
                                public views::ButtonListener {
  public:
-  InstalledBubbleContent(Extension* extension,
+  InstalledBubbleContent(const Extension* extension,
                          ExtensionInstalledBubble::BubbleType type,
                          SkBitmap* icon)
       : info_bubble_(NULL),
@@ -241,12 +241,13 @@ class InstalledBubbleContent : public views::View,
   DISALLOW_COPY_AND_ASSIGN(InstalledBubbleContent);
 };
 
-void ExtensionInstalledBubble::Show(Extension *extension, Browser *browser,
+void ExtensionInstalledBubble::Show(const Extension* extension,
+                                    Browser *browser,
                                     SkBitmap icon) {
   new ExtensionInstalledBubble(extension, browser, icon);
 }
 
-ExtensionInstalledBubble::ExtensionInstalledBubble(Extension *extension,
+ExtensionInstalledBubble::ExtensionInstalledBubble(const Extension* extension,
                                                    Browser *browser,
                                                    SkBitmap icon)
     : extension_(extension),
@@ -281,7 +282,7 @@ void ExtensionInstalledBubble::Observe(NotificationType type,
                                        const NotificationSource& source,
                                        const NotificationDetails& details) {
   if (type == NotificationType::EXTENSION_LOADED) {
-    Extension* extension = Details<Extension>(details).ptr();
+    const Extension* extension = Details<const Extension>(details).ptr();
     if (extension == extension_) {
       animation_wait_retries_ = 0;
       // PostTask to ourself to allow all EXTENSION_LOADED Observers to run.
diff --git a/chrome/browser/views/extensions/extension_installed_bubble.h b/chrome/browser/views/extensions/extension_installed_bubble.h
index 81c12a6..a35f820 100644
--- a/chrome/browser/views/extensions/extension_installed_bubble.h
+++ b/chrome/browser/views/extensions/extension_installed_bubble.h
@@ -44,13 +44,13 @@ class ExtensionInstalledBubble
   // the extension has loaded. |extension| is the installed extension. |browser|
   // is the browser window which will host the bubble. |icon| is the install
   // icon of the extension.
-  static void Show(Extension *extension, Browser *browser, SkBitmap icon);
+  static void Show(const Extension* extension, Browser *browser, SkBitmap icon);
 
  private:
   friend class base::RefCountedThreadSafe<ExtensionInstalledBubble>;
 
   // Private ctor. Registers a listener for EXTENSION_LOADED.
-  ExtensionInstalledBubble(Extension *extension, Browser *browser,
+  ExtensionInstalledBubble(const Extension* extension, Browser *browser,
                            SkBitmap icon);
 
   ~ExtensionInstalledBubble() {}
@@ -69,7 +69,7 @@ class ExtensionInstalledBubble
   virtual bool CloseOnEscape() { return true; }
   virtual bool FadeInOnShow() { return true; }
 
-  Extension* extension_;
+  const Extension* extension_;
   Browser* browser_;
   SkBitmap icon_;
   NotificationRegistrar registrar_;
diff --git a/chrome/browser/views/extensions/extension_view.cc b/chrome/browser/views/extensions/extension_view.cc
index 4ba38ca..fcace1a 100644
--- a/chrome/browser/views/extensions/extension_view.cc
+++ b/chrome/browser/views/extensions/extension_view.cc
@@ -39,7 +39,7 @@ ExtensionView::~ExtensionView() {
   CleanUp();
 }
 
-Extension* ExtensionView::extension() const {
+const Extension* ExtensionView::extension() const {
   return host_->extension();
 }
 
diff --git a/chrome/browser/views/extensions/extension_view.h b/chrome/browser/views/extensions/extension_view.h
index 6eded74a..037c2e8e 100644
--- a/chrome/browser/views/extensions/extension_view.h
+++ b/chrome/browser/views/extensions/extension_view.h
@@ -36,7 +36,7 @@ class ExtensionView : public views::NativeViewHost {
 
   ExtensionHost* host() const { return host_; }
   Browser* browser() const { return browser_; }
-  Extension* extension() const;
+  const Extension* extension() const;
   RenderViewHost* render_view_host() const;
   void DidStopLoading();
   void SetIsClipped(bool is_clipped);
diff --git a/chrome/browser/views/infobars/extension_infobar.cc b/chrome/browser/views/infobars/extension_infobar.cc
index 441a95e..e2fb43f 100644
--- a/chrome/browser/views/infobars/extension_infobar.cc
+++ b/chrome/browser/views/infobars/extension_infobar.cc
@@ -164,7 +164,7 @@ void ExtensionInfoBar::SetupIconAndMenu() {
   menu_->SetVisible(false);
   AddChildView(menu_);
 
-  Extension* extension = delegate_->extension_host()->extension();
+  const Extension* extension = delegate_->extension_host()->extension();
   ExtensionResource icon_resource = extension->GetIconResource(
       Extension::EXTENSION_ICON_BITTY, ExtensionIconSet::MATCH_EXACTLY);
   if (!icon_resource.relative_path().empty()) {
diff --git a/chrome/browser/views/location_bar/page_action_image_view.cc b/chrome/browser/views/location_bar/page_action_image_view.cc
index aa739c0..c7155bf 100644
--- a/chrome/browser/views/location_bar/page_action_image_view.cc
+++ b/chrome/browser/views/location_bar/page_action_image_view.cc
@@ -26,8 +26,8 @@ PageActionImageView::PageActionImageView(LocationBarView* owner,
       current_tab_id_(-1),
       preview_enabled_(false),
       popup_(NULL) {
-  Extension* extension = profile->GetExtensionsService()->GetExtensionById(
-      page_action->extension_id(), false);
+  const Extension* extension = profile->GetExtensionsService()->
+      GetExtensionById(page_action->extension_id(), false);
   DCHECK(extension);
 
   // Load all the icons declared in the manifest. This is the contents of the
@@ -146,8 +146,8 @@ bool PageActionImageView::OnKeyPressed(const views::KeyEvent& e) {
 
 void PageActionImageView::ShowContextMenu(const gfx::Point& p,
                                           bool is_mouse_gesture) {
-  Extension* extension = profile_->GetExtensionsService()->GetExtensionById(
-      page_action()->extension_id(), false);
+  const Extension* extension = profile_->GetExtensionsService()->
+      GetExtensionById(page_action()->extension_id(), false);
   Browser* browser = BrowserView::GetBrowserViewForNativeWindow(
       platform_util::GetTopLevel(GetWidget()->GetNativeView()))->browser();
   context_menu_contents_ =
diff --git a/chrome/common/extensions/extension.cc b/chrome/common/extensions/extension.cc
index 8bf9938..dc11856 100644
--- a/chrome/common/extensions/extension.cc
+++ b/chrome/common/extensions/extension.cc
@@ -299,7 +299,7 @@ int Extension::GetPermissionMessageId(const std::string& permission) {
   return ExtensionConfig::GetSingleton()->GetPermissionMessageId(permission);
 }
 
-std::vector<string16> Extension::GetPermissionMessages() {
+std::vector<string16> Extension::GetPermissionMessages() const {
   std::vector<string16> messages;
   if (!plugins().empty()) {
     messages.push_back(
@@ -317,7 +317,7 @@ std::vector<string16> Extension::GetPermissionMessages() {
   return messages;
 }
 
-std::set<string16> Extension::GetSimplePermissionMessages() {
+std::set<string16> Extension::GetSimplePermissionMessages() const {
   std::set<string16> messages;
   std::set<std::string>::const_iterator i;
   for (i = api_permissions().begin(); i != api_permissions().end(); ++i) {
@@ -328,7 +328,7 @@ std::set<string16> Extension::GetSimplePermissionMessages() {
   return messages;
 }
 
-std::vector<std::string> Extension::GetDistinctHosts() {
+std::vector<std::string> Extension::GetDistinctHosts() const {
   return GetDistinctHosts(GetEffectiveHostPermissions().patterns());
 }
 
@@ -359,7 +359,7 @@ std::vector<std::string> Extension::GetDistinctHosts(
   return distinct_hosts;
 }
 
-string16 Extension::GetHostPermissionMessage() {
+string16 Extension::GetHostPermissionMessage() const {
   if (HasEffectiveAccessToAllHosts())
     return l10n_util::GetStringUTF16(IDS_EXTENSION_PROMPT2_WARNING_ALL_HOSTS);
 
@@ -447,7 +447,7 @@ std::string Extension::GenerateIdForPath(const FilePath& path) {
   return id;
 }
 
-Extension::HistogramType Extension::GetHistogramType() {
+Extension::HistogramType Extension::GetHistogramType() const {
   if (is_theme())
     return TYPE_THEME;
   if (converted_from_user_script())
@@ -782,7 +782,7 @@ ExtensionAction* Extension::LoadExtensionActionHelper(
   return result.release();
 }
 
-bool Extension::ContainsNonThemeKeys(const DictionaryValue& source) {
+bool Extension::ContainsNonThemeKeys(const DictionaryValue& source) const {
   for (DictionaryValue::key_iterator key = source.begin_keys();
        key != source.end_keys(); ++key) {
     if (!IsBaseCrxKey(*key) && *key != keys::kTheme)
@@ -1019,7 +1019,8 @@ Extension::Extension(const FilePath& path, Location location)
 Extension::~Extension() {
 }
 
-ExtensionResource Extension::GetResource(const std::string& relative_path) {
+ExtensionResource Extension::GetResource(
+    const std::string& relative_path) const {
 #if defined(OS_POSIX)
   FilePath relative_file_path(relative_path);
 #elif defined(OS_WIN)
@@ -1028,7 +1029,8 @@ ExtensionResource Extension::GetResource(const std::string& relative_path) {
   return ExtensionResource(id(), path(), relative_file_path);
 }
 
-ExtensionResource Extension::GetResource(const FilePath& relative_file_path) {
+ExtensionResource Extension::GetResource(
+    const FilePath& relative_file_path) const {
   return ExtensionResource(id(), path(), relative_file_path);
 }
 
@@ -1108,8 +1110,8 @@ bool Extension::FormatPEMForFileOutput(const std::string input,
 // extensions that require less permissions than the current version, but then
 // we don't silently allow them to go back. In order to fix this, we would need
 // to remember the max set of permissions we ever granted a single extension.
-bool Extension::IsPrivilegeIncrease(Extension* old_extension,
-                                    Extension* new_extension) {
+bool Extension::IsPrivilegeIncrease(const Extension* old_extension,
+                                    const Extension* new_extension) {
   // If the old extension had native code access, we don't need to go any
   // further. Things can't get any worse.
   if (old_extension->plugins().size() > 0)
@@ -1156,7 +1158,7 @@ bool Extension::IsPrivilegeIncrease(Extension* old_extension,
 }
 
 // static
-void Extension::DecodeIcon(Extension* extension,
+void Extension::DecodeIcon(const Extension* extension,
                            Icons icon_size,
                            scoped_ptr<SkBitmap>* result) {
   FilePath icon_path = extension->GetIconResource(
@@ -1899,7 +1901,7 @@ GURL Extension::GetHomepageURL() const {
   return url;
 }
 
-std::set<FilePath> Extension::GetBrowserImages() {
+std::set<FilePath> Extension::GetBrowserImages() const {
   std::set<FilePath> image_paths;
   // TODO(viettrungluu): These |FilePath::FromWStringHack(UTF8ToWide())|
   // indicate that we're doing something wrong.
@@ -1949,12 +1951,12 @@ GURL Extension::GetFullLaunchURL() const {
     return GURL(launch_web_url());
 }
 
-bool Extension::GetBackgroundPageReady() {
+bool Extension::GetBackgroundPageReady() const {
   return (GetRuntimeData()->background_page_ready ||
           background_url().is_empty());
 }
 
-void Extension::SetBackgroundPageReady() {
+void Extension::SetBackgroundPageReady() const {
   DCHECK(!background_url().is_empty());
   GetRuntimeData()->background_page_ready = true;
   NotificationService::current()->Notify(
@@ -1982,7 +1984,7 @@ void Extension::SetScriptingWhitelist(
 
 void Extension::SetCachedImage(const ExtensionResource& source,
                                const SkBitmap& image,
-                               const gfx::Size& original_size) {
+                               const gfx::Size& original_size) const {
   DCHECK(source.extension_root() == path());  // The resource must come from
                                               // this extension.
   const FilePath& path = source.relative_path();
@@ -1997,14 +1999,14 @@ void Extension::SetCachedImage(const ExtensionResource& source,
 }
 
 bool Extension::HasCachedImage(const ExtensionResource& source,
-                               const gfx::Size& max_size) {
+                               const gfx::Size& max_size) const {
   DCHECK(source.extension_root() == path());  // The resource must come from
                                               // this extension.
   return GetCachedImageImpl(source, max_size) != NULL;
 }
 
 SkBitmap Extension::GetCachedImage(const ExtensionResource& source,
-                                   const gfx::Size& max_size) {
+                                   const gfx::Size& max_size) const {
   DCHECK(source.extension_root() == path());  // The resource must come from
                                               // this extension.
   SkBitmap* image = GetCachedImageImpl(source, max_size);
@@ -2012,7 +2014,7 @@ SkBitmap Extension::GetCachedImage(const ExtensionResource& source,
 }
 
 SkBitmap* Extension::GetCachedImageImpl(const ExtensionResource& source,
-                                        const gfx::Size& max_size) {
+                                        const gfx::Size& max_size) const {
   const FilePath& path = source.relative_path();
 
   // Look for exact size match.
@@ -2036,14 +2038,15 @@ SkBitmap* Extension::GetCachedImageImpl(const ExtensionResource& source,
 }
 
 ExtensionResource Extension::GetIconResource(
-    int size, ExtensionIconSet::MatchType match_type) {
+    int size, ExtensionIconSet::MatchType match_type) const {
   std::string path = icons().Get(size, match_type);
   if (path.empty())
     return ExtensionResource();
   return GetResource(path);
 }
 
-GURL Extension::GetIconURL(int size, ExtensionIconSet::MatchType match_type) {
+GURL Extension::GetIconURL(int size,
+                           ExtensionIconSet::MatchType match_type) const {
   std::string path = icons().Get(size, match_type);
   if (path.empty())
     return GURL();
@@ -2064,7 +2067,7 @@ bool Extension::CanSpecifyHostPermission(const URLPattern& pattern) const {
   return true;
 }
 
-// static.
+// static
 bool Extension::HasApiPermission(
     const std::set<std::string>& api_permissions,
     const std::string& function_name) {
@@ -2204,7 +2207,7 @@ bool Extension::HasEffectiveAccessToAllHosts() const {
   return false;
 }
 
-bool Extension::IsAPIPermission(const std::string& str) {
+bool Extension::IsAPIPermission(const std::string& str) const {
   for (size_t i = 0; i < Extension::kNumPermissions; ++i) {
     if (str == Extension::kPermissions[i].name) {
       // Only allow the experimental API permission if the command line
diff --git a/chrome/common/extensions/extension.h b/chrome/common/extensions/extension.h
index 82c007b..08e4bbb 100644
--- a/chrome/common/extensions/extension.h
+++ b/chrome/common/extensions/extension.h
@@ -285,7 +285,7 @@ class Extension : public base::RefCountedThreadSafe<Extension> {
 
   // Returns the full list of permission messages that this extension
   // should display at install time.
-  std::vector<string16> GetPermissionMessages();
+  std::vector<string16> GetPermissionMessages() const;
 
   // Returns the distinct hosts that should be displayed in the install UI. This
   // discards some of the detail that is present in the manifest to make it as
@@ -293,7 +293,7 @@ class Extension : public base::RefCountedThreadSafe<Extension> {
   // and path components of URLPatterns and de-dupe the result.
   static std::vector<std::string> GetDistinctHosts(
       const URLPatternList& host_patterns);
-  std::vector<std::string> GetDistinctHosts();
+  std::vector<std::string> GetDistinctHosts() const;
 
   // Icon sizes used by the extension system.
   static const int kIconSizes[];
@@ -378,7 +378,7 @@ class Extension : public base::RefCountedThreadSafe<Extension> {
   }
 
   // See HistogramType definition above.
-  HistogramType GetHistogramType();
+  HistogramType GetHistogramType() const;
 
   // Returns an absolute url to a resource inside of an extension. The
   // |extension_url| argument should be the url() from an Extension object. The
@@ -393,10 +393,10 @@ class Extension : public base::RefCountedThreadSafe<Extension> {
 
   // Returns an extension resource object. |relative_path| should be UTF8
   // encoded.
-  ExtensionResource GetResource(const std::string& relative_path);
+  ExtensionResource GetResource(const std::string& relative_path) const;
 
   // As above, but with |relative_path| following the file system's encoding.
-  ExtensionResource GetResource(const FilePath& relative_path);
+  ExtensionResource GetResource(const FilePath& relative_path) const;
 
   // |input| is expected to be the text of an rsa public or private key. It
   // tolerates the presence or absence of bracking header/footer like this:
@@ -418,14 +418,14 @@ class Extension : public base::RefCountedThreadSafe<Extension> {
 
   // Determine whether |new_extension| has increased privileges compared to
   // |old_extension|.
-  static bool IsPrivilegeIncrease(Extension* old_extension,
-                                  Extension* new_extension);
+  static bool IsPrivilegeIncrease(const Extension* old_extension,
+                                  const Extension* new_extension);
 
   // Given an extension and icon size, read it if present and decode it into
   // result. In the browser process, this will DCHECK if not called on the
   // file thread. To easily load extension images on the UI thread, see
   // ImageLoadingTracker.
-  static void DecodeIcon(Extension* extension,
+  static void DecodeIcon(const Extension* extension,
                          Icons icon_size,
                          scoped_ptr<SkBitmap>* result);
 
@@ -560,12 +560,12 @@ class Extension : public base::RefCountedThreadSafe<Extension> {
 
   // Returns a list of paths (relative to the extension dir) for images that
   // the browser might load (like themes and page action icons).
-  std::set<FilePath> GetBrowserImages();
+  std::set<FilePath> GetBrowserImages() const;
 
   // Get an extension icon as a resource or URL.
-  ExtensionResource GetIconResource(int size,
-                                    ExtensionIconSet::MatchType match_type);
-  GURL GetIconURL(int size, ExtensionIconSet::MatchType match_type);
+  ExtensionResource GetIconResource(
+      int size, ExtensionIconSet::MatchType match_type) const;
+  GURL GetIconURL(int size, ExtensionIconSet::MatchType match_type) const;
 
   const DictionaryValue* manifest_value() const {
     return static_data_->manifest_value.get();
@@ -609,13 +609,13 @@ class Extension : public base::RefCountedThreadSafe<Extension> {
   // Whether the background page, if any, is ready. We don't load other
   // components until then. If there is no background page, we consider it to
   // be ready.
-  bool GetBackgroundPageReady();
-  void SetBackgroundPageReady();
+  bool GetBackgroundPageReady() const;
+  void SetBackgroundPageReady() const;
 
   // Getter and setter for the flag that specifies whether the extension is
   // being upgraded.
   bool being_upgraded() const { return GetRuntimeData()->being_upgraded; }
-  void set_being_upgraded(bool value) {
+  void set_being_upgraded(bool value) const {
     GetRuntimeData()->being_upgraded = value;
   }
 
@@ -625,11 +625,11 @@ class Extension : public base::RefCountedThreadSafe<Extension> {
   // before any scaling may have been done to produce the pixels in |image|.
   void SetCachedImage(const ExtensionResource& source,
                       const SkBitmap& image,
-                      const gfx::Size& original_size);
+                      const gfx::Size& original_size) const;
   bool HasCachedImage(const ExtensionResource& source,
-                      const gfx::Size& max_size);
+                      const gfx::Size& max_size) const;
   SkBitmap GetCachedImage(const ExtensionResource& source,
-                          const gfx::Size& max_size);
+                          const gfx::Size& max_size) const;
   bool is_hosted_app() const { return is_app() && !web_extent().is_empty(); }
   bool is_packaged_app() const { return is_app() && web_extent().is_empty(); }
 
@@ -658,7 +658,7 @@ class Extension : public base::RefCountedThreadSafe<Extension> {
   // value of NULL means there is no matching image cached (we allow caching an
   // empty SkBitmap).
   SkBitmap* GetCachedImageImpl(const ExtensionResource& source,
-                               const gfx::Size& max_size);
+                               const gfx::Size& max_size) const;
 
   // Helper method that loads a UserScript object from a
   // dictionary in the content_script list of the manifest.
@@ -700,21 +700,21 @@ class Extension : public base::RefCountedThreadSafe<Extension> {
 
   // Figures out if a source contains keys not associated with themes - we
   // don't want to allow scripts and such to be bundled with themes.
-  bool ContainsNonThemeKeys(const DictionaryValue& source);
+  bool ContainsNonThemeKeys(const DictionaryValue& source) const;
 
   // Returns true if the string is one of the known api permissions (see
   // kPermissions).
-  bool IsAPIPermission(const std::string& permission);
+  bool IsAPIPermission(const std::string& permission) const;
 
   // The set of unique API install messages that the extension has.
   // NOTE: This only includes messages related to permissions declared in the
   // "permissions" key in the manifest.  Permissions implied from other features
   // of the manifest, like plugins and content scripts are not included.
-  std::set<string16> GetSimplePermissionMessages();
+  std::set<string16> GetSimplePermissionMessages() const;
 
   // The permission message displayed related to the host permissions for
   // this extension.
-  string16 GetHostPermissionMessage();
+  string16 GetHostPermissionMessage() const;
 
   // Returns a mutable pointer to our runtime data. Can only be called on
   // the UI thread.
@@ -739,7 +739,7 @@ class Extension : public base::RefCountedThreadSafe<Extension> {
   DISALLOW_COPY_AND_ASSIGN(Extension);
 };
 
-typedef std::vector< scoped_refptr<Extension> > ExtensionList;
+typedef std::vector< scoped_refptr<const Extension> > ExtensionList;
 typedef std::set<std::string> ExtensionIdSet;
 
 // Handy struct to pass core extension info around.
diff --git a/chrome/test/testing_profile.h b/chrome/test/testing_profile.h
index 55ca1df..7cbe718 100644
--- a/chrome/test/testing_profile.h
+++ b/chrome/test/testing_profile.h
@@ -201,10 +201,10 @@ class TestingProfile : public Profile {
   virtual BrowserSignin* GetBrowserSignin() { return NULL; }
   virtual bool HasCreatedDownloadManager() const { return false; }
   virtual void InitThemes();
-  virtual void SetTheme(Extension* extension) {}
+  virtual void SetTheme(const Extension* extension) {}
   virtual void SetNativeTheme() {}
   virtual void ClearTheme() {}
-  virtual Extension* GetTheme() { return NULL; }
+  virtual const Extension* GetTheme() { return NULL; }
   virtual BrowserThemeProvider* GetThemeProvider() {
     InitThemes();
     return theme_provider_.get();