Keep the GCM data intact when the user signs out of the profile

components/gcm_driver/fake_gcm_client.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_FAKE_GCM_CLIENT_H_
 #define COMPONENTS_GCM_DRIVER_FAKE_GCM_CLIENT_H_
 
 #include "base/compiler_specific.h"
 #include "base/memory/weak_ptr.h"
 #include "components/gcm_driver/gcm_client.h"
@@ skipping 54 matching lines @@
   // Initiate the loading that has been delayed.
   // Called on UI thread.
   void PerformDelayedLoading();
 
   // Simulate receiving something from the server.
   // Called on UI thread.
   void ReceiveMessage(const std::string& app_id,
                       const IncomingMessage& message);
   void DeleteMessages(const std::string& app_id);
 
-  static std::string GetRegistrationIdFromSenderIds(
-      const std::vector<std::string>& sender_ids);
+  std::string GetRegistrationIdFromSenderIds(
+      const std::vector<std::string>& sender_ids) const;
 
   Status status() const { return status_; }
 
  private:
   // Called on IO thread.
   void DoLoading();
   void CheckinFinished();
   void RegisterFinished(const std::string& app_id,
                         const std::string& registrion_id);
   void UnregisterFinished(const std::string& app_id);
   void SendFinished(const std::string& app_id, const OutgoingMessage& message);
   void MessageReceived(const std::string& app_id,
                        const IncomingMessage& message);
   void MessagesDeleted(const std::string& app_id);
   void MessageSendError(const std::string& app_id,
                         const SendErrorDetails& send_error_details);
   void SendAcknowledgement(const std::string& app_id,
                            const std::string& message_id);
 
   Delegate* delegate_;
+  // Increased at checkout in order to produce a different registration ID
+  // after checkout and re-checkin.
+  int sequence_id_;
   Status status_;
   StartMode start_mode_;
   scoped_refptr<base::SequencedTaskRunner> ui_thread_;
   scoped_refptr<base::SequencedTaskRunner> io_thread_;
   base::WeakPtrFactory<FakeGCMClient> weak_ptr_factory_;
 
   DISALLOW_COPY_AND_ASSIGN(FakeGCMClient);
 };
 
 }  // namespace gcm
 
 #endif  // COMPONENTS_GCM_DRIVER_FAKE_GCM_CLIENT_H_