[MD settings] advanced font settings extension link

chrome/browser/resources/settings/appearance_page/fonts_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 {{
  *   fontList: Array<{0: string, 1: (string|undefined), 2: (string|undefined)}>,
  *   encodingList: Array<{0: string, 1: string}>,
+ *   extensionUrl: string
  * }}
  */
 var FontsData;
 
 cr.define('settings', function() {
   /** @interface */
   function FontsBrowserProxy() {}
 
   FontsBrowserProxy.prototype = {
     /**
-     * @return {!Promise<!FontsData>} Fonts and encodings.
+     * @return {!Promise<!FontsData>} Fonts, encodings and the advanced font
+     *     settings extension URL.
      */
     fetchFontsData: assertNotReached,
+
+    observeAdvancedFontExtensionAvailable: assertNotReached,
+
+    openAdvancedFontSettings: assertNotReached,
   };
 
   /**
    * @implements {settings.FontsBrowserProxy}
    * @constructor
    */
   function FontsBrowserProxyImpl() {}
 
   cr.addSingletonGetter(FontsBrowserProxyImpl);
 
   FontsBrowserProxyImpl.prototype = {
     /** @override */
     fetchFontsData: function() {
       return cr.sendWithPromise('fetchFontsData');
     },
+
+    /** @override */
+    observeAdvancedFontExtensionAvailable: function() {
+      chrome.send('observeAdvancedFontExtensionAvailable');
+    },
+
+    /** @override */
+    openAdvancedFontSettings: function() {
+      chrome.send('openAdvancedFontSettings');
+    }
   };
 
   return {
     FontsBrowserProxy: FontsBrowserProxy,
     FontsBrowserProxyImpl: FontsBrowserProxyImpl,
   };
 });