Persist Directory to disk when the app is backgrounded.

chrome/browser/sync/profile_sync_service.cc

 // 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.
 
 #include "chrome/browser/sync/profile_sync_service.h"
 
 #include <cstddef>
 #include <map>
 #include <vector>
 
@@ skipping 2711 matching lines @@
                  true));
 }
 
 bool ProfileSyncService::NeedBackup() const {
   return need_backup_;
 }
 
 base::Time ProfileSyncService::GetDeviceBackupTimeForTesting() const {
   return device_info_sync_service_->GetLocalDeviceBackupTime();
 }
+
+void ProfileSyncService::FlushDirectory() const {
+  // backend_initialized_ implies backend_ isn't NULL and the manager exists.
+  // If sync is not initialized yet, we fail silently.
+  if (backend_initialized_)
+    backend_->FlushDirectory();
+}