sync: Gracefully handle very early shutdown

sync/internal_api/sync_manager_impl.h

Index: sync/internal_api/sync_manager_impl.h
diff --git a/sync/internal_api/sync_manager_impl.h b/sync/internal_api/sync_manager_impl.h
index 712c268335ee7da5b026fdf9eecb3ece81a90be5..b4dac244064566134e8ec9a12b2f7fc61482d4ec 100644
--- a/sync/internal_api/sync_manager_impl.h
+++ b/sync/internal_api/sync_manager_impl.h
@@ -81,7 +81,8 @@ class SYNC_EXPORT_PRIVATE SyncManagerImpl :
       scoped_ptr<UnrecoverableErrorHandler> unrecoverable_error_handler,
       ReportUnrecoverableErrorFunction
           report_unrecoverable_error_function,
-      bool use_oauth2_token) OVERRIDE;
+      bool use_oauth2_token,
+      CancellationSignal* cancellation_signal) OVERRIDE;
   virtual void ThrowUnrecoverableError() OVERRIDE;
   virtual ModelTypeSet InitialSyncEndedTypes() OVERRIDE;
   virtual ModelTypeSet GetTypesWithEmptyProgressMarkerToken(
@@ -106,7 +107,6 @@ class SYNC_EXPORT_PRIVATE SyncManagerImpl :
   virtual void RemoveObserver(SyncManager::Observer* observer) OVERRIDE;
   virtual SyncStatus GetDetailedStatus() const OVERRIDE;
   virtual void SaveChanges() OVERRIDE;
-  virtual void StopSyncingForShutdown() OVERRIDE;
   virtual void ShutdownOnSyncThread() OVERRIDE;
   virtual UserShare* GetUserShare() OVERRIDE;
   virtual const std::string cache_guid() OVERRIDE;