[Sync] Fix auth error handling while the backend is initializing.

chrome/browser/sync/glue/sync_backend_host.h

 // Copyright (c) 2012 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 CHROME_BROWSER_SYNC_GLUE_SYNC_BACKEND_HOST_H_
 #define CHROME_BROWSER_SYNC_GLUE_SYNC_BACKEND_HOST_H_
 
 #include <string>
 
 #include "base/basictypes.h"
@@ skipping 163 matching lines @@
       const syncer::WeakHandle<syncer::JsEventHandler>& event_handler,
       const GURL& service_url,
       const syncer::SyncCredentials& credentials,
       bool delete_sync_data_folder,
       syncer::SyncManagerFactory* sync_manager_factory,
       syncer::UnrecoverableErrorHandler* unrecoverable_error_handler,
       syncer::ReportUnrecoverableErrorFunction
           report_unrecoverable_error_function);
 
   // Called on |frontend_loop| to update SyncCredentials.
-  void UpdateCredentials(const syncer::SyncCredentials& credentials);
+  virtual void UpdateCredentials(const syncer::SyncCredentials& credentials);
 
   // Registers the underlying frontend for the given IDs to the underlying
   // notifier.  This lasts until StopSyncingForShutdown() is called.
   void UpdateRegisteredInvalidationIds(const syncer::ObjectIdSet& ids);
 
   // This starts the SyncerThread running a Syncer object to communicate with
   // sync servers.  Until this is called, no changes will leave or enter this
   // browser from the cloud / sync servers.
   // Called on |frontend_loop_|.
   virtual void StartSyncingWithServer();
@@ skipping 356 matching lines @@
   // HandleInitializationCompletedOnFrontendLoop.
   syncer::WeakHandle<syncer::JsBackend> js_backend_;
   syncer::WeakHandle<syncer::DataTypeDebugInfoListener> debug_info_listener_;
 
   DISALLOW_COPY_AND_ASSIGN(SyncBackendHost);
 };
 
 }  // namespace browser_sync
 
 #endif  // CHROME_BROWSER_SYNC_GLUE_SYNC_BACKEND_HOST_H_