Create top level apps component and move some apps code there.

apps/app_restore_service.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_EXTENSIONS_APP_RESTORE_SERVICE_H_
 #define CHROME_BROWSER_EXTENSIONS_APP_RESTORE_SERVICE_H_
 
+#include <string>
+
 #include "chrome/browser/profiles/profile_keyed_service.h"
 #include "content/public/browser/notification_observer.h"
 #include "content/public/browser/notification_registrar.h"
 
-#include <string>
-
 class Profile;
 
 namespace extensions {
+class Extension;
+}
 
-class Extension;
+namespace apps {
 
 // Tracks what apps need to be restarted when the browser restarts.
 class AppRestoreService : public ProfileKeyedService,
                           public content::NotificationObserver {
  public:
   explicit AppRestoreService(Profile* profile);
 
   // Restart apps that need to be restarted and clear the "running" preference
   // from apps to prevent them being restarted in subsequent restarts.
   void HandleStartup(bool should_restore_apps);
 
  private:
   // content::NotificationObserver.
   virtual void Observe(int type,
                        const content::NotificationSource& source,
                        const content::NotificationDetails& details) OVERRIDE;
 
   void RecordAppStart(const std::string& extension_id);
   void RecordAppStop(const std::string& extension_id);
-  void RestoreApp(const Extension* extension);
+  void RestoreApp(const extensions::Extension* extension);
 
   content::NotificationRegistrar registrar_;
   Profile* profile_;
 };
 
-}  // namespace extensions
+}  // namespace apps
 
 #endif  // CHROME_BROWSER_EXTENSIONS_APP_RESTORE_SERVICE_H_