Make GCMDriver::GetInstanceIDHandler protected, to avoid misuse

components/gcm_driver/gcm_driver.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_H_
 #define COMPONENTS_GCM_DRIVER_GCM_DRIVER_H_
 
 #include <map>
 #include <string>
 #include <vector>
@@ skipping 194 matching lines @@
   virtual void RemoveAccountMapping(const std::string& account_id) = 0;
 
   // Getter and setter of last token fetch time.
   virtual base::Time GetLastTokenFetchTime() = 0;
   virtual void SetLastTokenFetchTime(const base::Time& time) = 0;
 
   // Sets whether or not GCM should try to wake the system from suspend in order
   // to send a heartbeat message.
   virtual void WakeFromSuspendForHeartbeat(bool wake) = 0;
 
-  // Supports InstanceID handling.
-  virtual InstanceIDHandler* GetInstanceIDHandler() = 0;
+  // Supports InstanceID handling. Must only be used by the InstanceID system.
+  virtual InstanceIDHandler* GetInstanceIDHandlerInternal() = 0;
 
   // Adds or removes a custom client requested heartbeat interval. If multiple
   // components set that setting, the lowest setting will be used. If the
   // setting is outside of GetMax/MinClientHeartbeatIntervalMs() it will be
   // ignored. If a new setting is less than the currently used, the connection
   // will be reset with the new heartbeat. Client that no longer require
   // aggressive heartbeats, should remove their requested interval. Heartbeats
   // set this way survive connection/Chrome restart.
   //
   // GCM Driver can decide to postpone the action until Client is properly
@@ skipping 107 matching lines @@
   DefaultGCMAppHandler default_app_handler_;
 
   base::WeakPtrFactory<GCMDriver> weak_ptr_factory_;
 
   DISALLOW_COPY_AND_ASSIGN(GCMDriver);
 };
 
 }  // namespace gcm
 
 #endif  // COMPONENTS_GCM_DRIVER_GCM_DRIVER_H_