[sync] Set up notification-free infra for triggering local sync refresh

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 59 matching lines @@
       const syncer::SyncCredentials& credentials,
       bool delete_sync_data_folder,
       scoped_ptr<syncer::SyncManagerFactory> sync_manager_factory,
       const syncer::WeakHandle<syncer::UnrecoverableErrorHandler>&
           unrecoverable_error_handler,
       const base::Closure& report_unrecoverable_error_function,
       syncer::NetworkResources* network_resources,
       scoped_ptr<syncer::SyncEncryptionHandler::NigoriState>
           saved_nigori_state) = 0;
 
+  // Called on the frontend's thread to trigger a refresh.
+  virtual void TriggerRefresh(const syncer::ModelTypeSet& types) = 0;
+
   // Called on the frontend's thread to update SyncCredentials.
   virtual void UpdateCredentials(
       const syncer::SyncCredentials& credentials) = 0;
 
   // 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() = 0;
 
@@ skipping 137 matching lines @@
   // See SyncManager::ClearServerData.
   virtual void ClearServerData(
       const syncer::SyncManager::ClearServerDataCallback& callback) = 0;
 
   DISALLOW_COPY_AND_ASSIGN(SyncBackendHost);
 };
 
 }  // namespace browser_sync
 
 #endif  // CHROME_BROWSER_SYNC_GLUE_SYNC_BACKEND_HOST_H_