Change to pass by const reference for a couple GCMDriverDesktop methods

components/gcm_driver/gcm_driver_desktop.h

 // Copyright 2014 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 COMPONENTS_GCM_DRIVER_GCM_DRIVER_DESKTOP_H_
 #define COMPONENTS_GCM_DRIVER_GCM_DRIVER_DESKTOP_H_
 
 #include <map>
 #include <string>
 #include <vector>
@@ skipping 102 matching lines @@
 
   // Callbacks posted from IO thread to UI thread.
   void RegisterFinished(const std::string& app_id,
                         const std::string& registration_id,
                         GCMClient::Result result);
   void UnregisterFinished(const std::string& app_id, GCMClient::Result result);
   void SendFinished(const std::string& app_id,
                     const std::string& message_id,
                     GCMClient::Result result);
   void MessageReceived(const std::string& app_id,
-                       GCMClient::IncomingMessage message);
+                       const GCMClient::IncomingMessage& message);
   void MessagesDeleted(const std::string& app_id);
   void MessageSendError(const std::string& app_id,
                         const GCMClient::SendErrorDetails& send_error_details);
   void GCMClientReady();
 
-  void GetGCMStatisticsFinished(GCMClient::GCMStatistics stats);
+  void GetGCMStatisticsFinished(const GCMClient::GCMStatistics& stats);
 
   // Flag to indicate if GCM is enabled.
   bool gcm_enabled_;
 
   // Flag to indicate if GCMClient is ready.
   bool gcm_client_ready_;
 
   // The account ID that this service is responsible for. Empty when the service
   // is not running.
   std::string account_id_;
@@ skipping 22 matching lines @@
 
   // Used to pass a weak pointer to the IO worker.
   base::WeakPtrFactory<GCMDriverDesktop> weak_ptr_factory_;
 
   DISALLOW_COPY_AND_ASSIGN(GCMDriverDesktop);
 };
 
 }  // namespace gcm
 
 #endif  // COMPONENTS_GCM_DRIVER_GCM_DRIVER_DESKTOP_H_