Add extensions code to use common updater in components/update_client/

extensions/browser/updater/update_client_config.cc

+// Copyright 2015 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 "extensions/browser/updater/update_client_config.h"
+
+#include "content/public/browser/browser_thread.h"
+
+namespace extensions {
+
+UpdateClientConfig::UpdateClientConfig() {}
+
+scoped_refptr<base::SequencedTaskRunner>
+UpdateClientConfig::GetSequencedTaskRunner() const {
+  return content::BrowserThread::GetBlockingPool()
+      ->GetSequencedTaskRunnerWithShutdownBehavior(
+          content::BrowserThread::GetBlockingPool()->GetSequenceToken(),
+          base::SequencedWorkerPool::SKIP_ON_SHUTDOWN);
+}
+
+scoped_refptr<base::SingleThreadTaskRunner>
+UpdateClientConfig::GetSingleThreadTaskRunner() const {
+  return content::BrowserThread::GetMessageLoopProxyForThread(
+      content::BrowserThread::FILE);
+}
+
+UpdateClientConfig::~UpdateClientConfig() {}
+
+}  // namespace extensions