Make GCMDriver::GetInstanceIDHandler protected, to avoid misuse

components/gcm_driver/instance_id/instance_id_impl.h

Index: components/gcm_driver/instance_id/instance_id_impl.h
diff --git a/components/gcm_driver/instance_id/instance_id_impl.h b/components/gcm_driver/instance_id/instance_id_impl.h
index 1f8749eb9056712daf876f4b6f9cf01f19f5b32d..f2d65a3ded58ffa2fbbea707b3bc86a18a604cf8 100644
--- a/components/gcm_driver/instance_id/instance_id_impl.h
+++ b/components/gcm_driver/instance_id/instance_id_impl.h
@@ -43,8 +43,6 @@ class InstanceIDImpl : public InstanceID {
   void DeleteID(const DeleteIDCallback& callback) override;
 
  private:
-  gcm::InstanceIDHandler* GetInstanceIDHandler() const;
-
   void EnsureIDGenerated();
 
   void OnGetTokenCompleted(const GetTokenCallback& callback,
@@ -69,8 +67,6 @@ class InstanceIDImpl : public InstanceID {
                      const DeleteTokenCallback& callback);
   void DoDeleteID(const DeleteIDCallback& callback);
 
-  gcm::GCMDriver* gcm_driver_;  // Not owned.
-
   gcm::GCMDelayedTaskController delayed_task_controller_;
 
   // The generated Instance ID.