Remove dependency on BrowserThread::FILE from Sync code

chrome/browser/sync/glue/extension_setting_data_type_controller.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/glue/extension_setting_data_type_controller.h"
 
 #include "base/bind.h"
 #include "base/metrics/histogram_macros.h"
+#include "chrome/browser/extensions/api/storage/backend_task_runner.h"
 #include "chrome/browser/extensions/extension_service.h"
 #include "chrome/browser/profiles/profile.h"
 #include "components/sync/driver/generic_change_processor.h"
 #include "components/sync/model/syncable_service.h"
-#include "content/public/browser/browser_thread.h"
 #include "extensions/browser/extension_system.h"
 
-using content::BrowserThread;
-
 namespace browser_sync {
 
 ExtensionSettingDataTypeController::ExtensionSettingDataTypeController(
     syncer::ModelType type,
     const base::Closure& dump_stack,
     syncer::SyncClient* sync_client,
     Profile* profile)
-    : AsyncDirectoryTypeController(
-          type,
-          dump_stack,
-          sync_client,
-          syncer::GROUP_FILE,
-          BrowserThread::GetTaskRunnerForThread(BrowserThread::FILE)),
+    : AsyncDirectoryTypeController(type,
+                                   dump_stack,
+                                   sync_client,
+                                   syncer::GROUP_FILE,
+                                   extensions::GetBackendTaskRunner()),
       profile_(profile) {
   DCHECK(type == syncer::EXTENSION_SETTINGS || type == syncer::APP_SETTINGS);
 }
 
 ExtensionSettingDataTypeController::~ExtensionSettingDataTypeController() {}
 
 bool ExtensionSettingDataTypeController::StartModels() {
   DCHECK(CalledOnValidThread());
   extensions::ExtensionSystem::Get(profile_)->InitForRegularProfile(true);
   return true;
 }
 
 }  // namespace browser_sync