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

chrome/browser/ui/webui/extensions/command_handler.h

 // Copyright (c) 2012 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_EXTENSIONS_COMMAND_HANDLER_H_
 #define CHROME_BROWSER_UI_WEBUI_EXTENSIONS_COMMAND_HANDLER_H_
 
+#include "base/scoped_observer.h"
 #include "base/compiler_specific.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 DictionaryValue;
 class ListValue;
 }
 
 namespace content {
 class WebUIDataSource;
 }
 
 namespace extensions {
 class Command;
 class CommandService;
+class ExtensionRegistry;
 }
 
 class Extension;
 class Profile;
 
 namespace extensions {
 
 // The handler page for the Extension Commands UI overlay.
 class CommandHandler : public content::WebUIMessageHandler,
-                       public content::NotificationObserver {
+                       public extensions::ExtensionRegistryObserver {
  public:
   explicit CommandHandler(Profile* profile);
   virtual ~CommandHandler();
 
   // Fetches the localized values for the page and deposits them into |source|.
   void GetLocalizedValues(content::WebUIDataSource* source);
 
   // WebUIMessageHandler implementation.
   virtual void RegisterMessages() OVERRIDE;
 
-  // NotificationObserver implementation.
-  virtual void Observe(int type,
-                       const content::NotificationSource& source,
-                       const content::NotificationDetails& details) OVERRIDE;
+ private:
+  // extension::ExtensionRegistryObserver implementation.

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

nit: extensions::

+  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;
 
- private:
    // Update the list of extension commands in the config UI.
   void UpdateCommandDataOnPage();
 
   // Handles requests from javascript to fetch the extensions data, including
   // the commands it contains.
   // Replies back through: ExtensionCommandsOverlay.returnExtensionsData.
   void HandleRequestExtensionsData(const base::ListValue* args);
 
   // Handles requests from javascript to set a particular keyboard shortcut
   // for a given extension command.
   void HandleSetExtensionCommandShortcut(const base::ListValue* args);
 
   // Handles requests from javascript to change the scope of a particular
   // keyboard shortcut for a given extension command.
   void HandleSetCommandScope(const base::ListValue* args);
 
   // Handles requests from javascript to temporarily disable general Chrome
   // shortcut handling while the web page is capturing which shortcut to use.
   void HandleSetShortcutHandlingSuspended(const base::ListValue* args);
 
   // Fetches all known commands, active and inactive and returns them through
   // |commands|.
   void GetAllCommands(base::DictionaryValue* commands);
 
-  content::NotificationRegistrar registrar_;
+  Profile* profile_;
 
-  Profile* profile_;
+  ScopedObserver<extensions::ExtensionRegistry,
+                 extensions::ExtensionRegistryObserver>
+      extension_registry_observer_;
 
   DISALLOW_COPY_AND_ASSIGN(CommandHandler);
 };
 
 }  // namespace extensions
 
 #endif  // CHROME_BROWSER_UI_WEBUI_EXTENSIONS_COMMAND_HANDLER_H_