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

extensions/browser/updater/update_client_config.h

+// 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.
+
+#ifndef EXTENSIONS_BROWSER_UPDATER_UPDATE_CLIENT_CONFIG_H_
+#define EXTENSIONS_BROWSER_UPDATER_UPDATE_CLIENT_CONFIG_H_
+
+#include <string>
+
+#include "base/memory/ref_counted.h"
+#include "components/update_client/configurator.h"
+
+namespace base {
+class SequencedTaskRunner;
+class SingleThreadTaskRunner;
+}
+
+namespace extensions {
+
+// Used to provide configuration settings to the UpdateClient.
+class UpdateClientConfig : public update_client::Configurator {
+ public:
+  UpdateClientConfig();
+
+  scoped_refptr<base::SequencedTaskRunner> GetSequencedTaskRunner()
+      const override;
+  scoped_refptr<base::SingleThreadTaskRunner> GetSingleThreadTaskRunner()
+      const override;
+
+ protected:
+  friend class base::RefCountedThreadSafe<UpdateClientConfig>;
+  ~UpdateClientConfig() override;
+
+ private:
+  DISALLOW_COPY_AND_ASSIGN(UpdateClientConfig);
+};
+
+}  // namespace extensions
+
+#endif  // EXTENSIONS_BROWSER_UPDATER_UPDATE_CLIENT_CONFIG_H_