Use EventRouter::Get instead of ExtensionSystem::Get(browser_context)->event_router()

chrome/browser/ui/webui/app_list/start_page_handler.h

 // Copyright 2013 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #ifndef CHROME_BROWSER_UI_WEBUI_APP_LIST_START_PAGE_HANDLER_H_
 #define CHROME_BROWSER_UI_WEBUI_APP_LIST_START_PAGE_HANDLER_H_
 
 #include "base/basictypes.h"
 #include "base/compiler_specific.h"
+#include "base/scoped_observer.h"
 #include "base/prefs/pref_change_registrar.h"
 #include "chrome/browser/ui/app_list/recommended_apps_observer.h"
-#include "content/public/browser/notification_observer.h"
-#include "content/public/browser/notification_registrar.h"
 #include "content/public/browser/web_ui_message_handler.h"
+#include "extensions/browser/extension_registry_observer.h"
 
 namespace base {
 class ListValue;
 }
 
+namespace extensions {
+class ExtensionRegistry;
+}
+
 namespace app_list {
 
 class RecommendedApps;
 
 // Handler for the app launcher start page.
 class StartPageHandler : public content::WebUIMessageHandler,
-                         public content::NotificationObserver,
+                         public extensions::ExtensionRegistryObserver,
                          public RecommendedAppsObserver {
  public:
   StartPageHandler();
   virtual ~StartPageHandler();
 
  private:
   // content::WebUIMessageHandler overrides:
   virtual void RegisterMessages() OVERRIDE;
 
-  // Overridden from content::NotificationObserver:
-  virtual void Observe(int type,
-                       const content::NotificationSource& source,
-                       const content::NotificationDetails& details) OVERRIDE;
+  // extension::ExtensionRegistryObserver implementation.

[Devlin, 2014/05/16 17:34:04]

micro nit: extensions::, not extension::.

+  virtual void OnExtensionLoaded(
+      content::BrowserContext* browser_context,
+      const extensions::Extension* extension) OVERRIDE;
+  virtual void OnExtensionUnloaded(
+      content::BrowserContext* browser_context,
+      const extensions::Extension* extension,
+      extensions::UnloadedExtensionInfo::Reason reason) OVERRIDE;
 
   // RecommendedAppsObserver overrdies:
   virtual void OnRecommendedAppsChanged() OVERRIDE;
 
   // Creates a ListValue for the recommended apps and sends it to js side.
   void SendRecommendedApps();
 
 #if defined(OS_CHROMEOS)
   // Called when the pref has been changed.
   void OnHotwordEnabledChanged();
 #endif
 
   // JS callbacks.
   void HandleInitialize(const base::ListValue* args);
   void HandleLaunchApp(const base::ListValue* args);
   void HandleSpeechResult(const base::ListValue* args);
   void HandleSpeechSoundLevel(const base::ListValue* args);
   void HandleSpeechRecognition(const base::ListValue* args);
 
   RecommendedApps* recommended_apps_;  // Not owned.
   PrefChangeRegistrar pref_change_registrar_;
-  content::NotificationRegistrar registrar_;
+
+  ScopedObserver<extensions::ExtensionRegistry,
+                 extensions::ExtensionRegistryObserver>
+      extension_registry_observer_;
 
   DISALLOW_COPY_AND_ASSIGN(StartPageHandler);
 };
 
 }  // namespace app_list
 
 #endif  // CHROME_BROWSER_UI_WEBUI_APP_LIST_START_PAGE_HANDLER_H_