Migrate Extensions code to Task Scheduler API

chrome/browser/extensions/api/storage/settings_sync_util.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/extensions/api/storage/settings_sync_util.h"
 
 #include "base/json/json_writer.h"
 #include "base/values.h"
 #include "chrome/browser/extensions/api/storage/sync_value_store_cache.h"
 #include "components/sync/protocol/app_setting_specifics.pb.h"
 #include "components/sync/protocol/extension_setting_specifics.pb.h"
 #include "components/sync/protocol/sync.pb.h"
-#include "content/public/browser/browser_thread.h"
+#include "extensions/browser/api/storage/backend_task_runner.h"
 #include "extensions/browser/api/storage/storage_frontend.h"
 
-using content::BrowserThread;
-
 namespace extensions {
 
 namespace settings_sync_util {
 
 namespace {
 
 void PopulateExtensionSettingSpecifics(
     const std::string& extension_id,
     const std::string& key,
     const base::Value& value,
@@ skipping 77 matching lines @@
     syncer::ModelType type) {
   base::DictionaryValue no_value;
   return syncer::SyncChange(
       FROM_HERE,
       syncer::SyncChange::ACTION_DELETE,
       CreateData(extension_id, key, no_value, type));
 }
 
 syncer::SyncableService* GetSyncableService(content::BrowserContext* context,
                                             syncer::ModelType type) {
-  DCHECK_CURRENTLY_ON(BrowserThread::FILE);
+  DCHECK(IsOnBackendSequence());
   DCHECK(type == syncer::APP_SETTINGS || type == syncer::EXTENSION_SETTINGS);
   StorageFrontend* frontend = StorageFrontend::Get(context);
   SyncValueStoreCache* sync_cache = static_cast<SyncValueStoreCache*>(
       frontend->GetValueStoreCache(settings_namespace::SYNC));
   return sync_cache->GetSyncableService(type);
 }
 
 }  // namespace settings_sync_util
 
 }  // namespace extensions