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

extensions/browser/extensions_browser_client.cc

 // Copyright 2013 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/extensions_browser_client.h"
 
 #include "base/basictypes.h"
 #include "base/logging.h"
+#include "components/update_client/update_client.h"
 #include "extensions/browser/extension_error.h"
+#include "extensions/browser/updater/update_client_config.h"
 
 namespace extensions {
 
 namespace {
 
 ExtensionsBrowserClient* g_client = NULL;
 
 }  // namespace
 
+scoped_refptr<update_client::UpdateClient>
+ExtensionsBrowserClient::CreateUpdateClient(content::BrowserContext* context) {
+  return scoped_refptr<update_client::UpdateClient>(nullptr);
+}
+
 void ExtensionsBrowserClient::ReportError(content::BrowserContext* context,
                                           scoped_ptr<ExtensionError> error) {
   LOG(ERROR) << error->GetDebugString();
 }
 
 ExtensionsBrowserClient* ExtensionsBrowserClient::Get() {
   return g_client;
 }
 
 void ExtensionsBrowserClient::Set(ExtensionsBrowserClient* client) {
   g_client = client;
 }
 
 }  // namespace extensions