Notify GCMAppHandlers when the store is reset, so they clear cached IDs

components/gcm_driver/gcm_app_handler.h

 // Copyright (c) 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_APP_HANDLER_H_
 #define COMPONENTS_GCM_DRIVER_GCM_APP_HANDLER_H_
 
 #include <string>
 
 #include "components/gcm_driver/gcm_client.h"
 
 namespace gcm {
 
 // Defines the interface to provide handling and event routing logic for a given
 // app.
 class GCMAppHandler {
  public:
   GCMAppHandler();
   virtual ~GCMAppHandler();
 
   // Called to do all the cleanup when GCM is shutting down.
   // In the case that multiple apps share the same app handler, it should be
   // make safe for ShutdownHandler to be called multiple times.
   virtual void ShutdownHandler() = 0;
 
+  // Called when the GCM store is reset (e.g. due to corruption), which changes
+  // the device ID, invalidating all prior registrations. Any stored state
+  // related to GCM registrations or InstanceIDs should be deleted. This should
+  // only be considered a defense in depth, as this method will not be called if
+  // the store is reset before this app handler is registered; hence it is
+  // recommended to regularly revalidate any stored registrations/InstanceIDs.
+  // TODO(johnme): GCMDriver doesn't yet provide an API for revalidating them.
+  virtual void OnStoreReset() = 0;
+
   // Called when a GCM message has been received.
   virtual void OnMessage(const std::string& app_id,
                          const IncomingMessage& message) = 0;
 
   // Called when some GCM messages have been deleted from the server.
   virtual void OnMessagesDeleted(const std::string& app_id) = 0;
 
   // Called when a GCM message failed to be delivered.
   virtual void OnSendError(
       const std::string& app_id,
       const GCMClient::SendErrorDetails& send_error_details) = 0;
 
   // Called when a GCM message was received by GCM server.
   virtual void OnSendAcknowledged(const std::string& app_id,
                                   const std::string& message_id) = 0;
 
   // If no app handler has been added with the exact app_id of an incoming
   // event, all handlers will be asked (in arbitrary order) whether they can
   // handle the app_id, and the first to return true will receive the event.
   virtual bool CanHandle(const std::string& app_id) const;
 };
 
 }  // namespace gcm
 
 #endif  // COMPONENTS_GCM_DRIVER_GCM_APP_HANDLER_H_