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

extensions/browser/test_extensions_browser_client.cc

 // Copyright 2014 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/test_extensions_browser_client.h"
 
 #include "base/values.h"
 #include "content/public/browser/browser_context.h"
 #include "extensions/browser/extension_host_delegate.h"
 #include "extensions/browser/test_runtime_api_delegate.h"
@@ skipping 182 matching lines @@
     const std::string& min_version) {
   return true;
 }
 
 ExtensionWebContentsObserver*
 TestExtensionsBrowserClient::GetExtensionWebContentsObserver(
     content::WebContents* web_contents) {
   return nullptr;
 }
 
+scoped_refptr<update_client::UpdateClient>
+TestExtensionsBrowserClient::CreateUpdateClient(
+    content::BrowserContext* context) {
+  return update_client_.Pass();
+}
+
 }  // namespace extensions