Implement extension controlled indicators, starting with New Tab page

chrome/browser/resources/settings/on_startup_page/on_startup_browser_proxy.js

+// Copyright 2016 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.
+
+/** @typedef {{id: string, name: string, canBeDisabled: boolean}} */
+var NtpExtension;
+
+cr.define('settings', function() {
+  /** @interface */
+  function OnStartupBrowserProxy() {}
+
+  OnStartupBrowserProxy.prototype = {
+    /** @return {!Promise<?NtpExtension>} */
+    getNtpExtension: assertNotReached,
+  };
+
+  /**
+   * @constructor
+   * @implements {settings.OnStartupBrowserProxy}
+   */
+  function OnStartupBrowserProxyImpl() {}
+  cr.addSingletonGetter(OnStartupBrowserProxyImpl);
+
+  OnStartupBrowserProxyImpl.prototype = {
+    /** @override */
+    getNtpExtension: function() {
+      return cr.sendWithPromise('getNtpExtension');
+    },
+  };
+
+  return {
+    OnStartupBrowserProxy: OnStartupBrowserProxy,
+    OnStartupBrowserProxyImpl: OnStartupBrowserProxyImpl,
+  };
+});