[GCM] Observe the event listener adding such that GCM can be started

chrome/browser/services/gcm/gcm_profile_service.h

 // Copyright (c) 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_SERVICES_GCM_GCM_PROFILE_SERVICE_H_
 #define CHROME_BROWSER_SERVICES_GCM_GCM_PROFILE_SERVICE_H_
 
 #include <map>
 
 #include "base/basictypes.h"
@@ skipping 60 matching lines @@
 
   explicit GCMProfileService(Profile* profile);
   virtual ~GCMProfileService();
 
   void Initialize(scoped_ptr<GCMClientFactory> gcm_client_factory);
 
   void Start();
 
   void Stop();
 
+  // BrowserContextKeyedService implementation.
+  virtual void Shutdown() OVERRIDE;
+
   // Registers |sender_id| for an app. A registration ID will be returned by
   // the GCM server.
   // |app_id|: application ID.
   // |sender_ids|: list of IDs of the servers that are allowed to send the
   //               messages to the application. These IDs are assigned by the
   //               Google API Console.
   // |callback|: to be called once the asynchronous operation is done.
   virtual void Register(const std::string& app_id,
                         const std::vector<std::string>& sender_ids,
                         RegisterCallback callback);
@@ skipping 134 matching lines @@
 
   // Used to pass a weak pointer to the IO worker.
   base::WeakPtrFactory<GCMProfileService> weak_ptr_factory_;
 
   DISALLOW_COPY_AND_ASSIGN(GCMProfileService);
 };
 
 }  // namespace gcm
 
 #endif  // CHROME_BROWSER_SERVICES_GCM_GCM_PROFILE_SERVICE_H_