Update iOS WebUI History to use icon.js

ui/webui/resources/js/icon.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.
 
 cr.define('cr.icon', function() {
   /**
    * @return {!Array<number>} The scale factors supported by this platform for
    *     webui resources.
    */
   function getSupportedScaleFactors() {
@@ skipping 80 matching lines @@
     var type = opt_type || 'favicon';
 
     return imageset(
         'chrome://' + type + '/size/' + size + '@scalefactorx/' +
         // Note: Literal 'iconurl' must match |kIconURLParameter| in
         // components/favicon_base/favicon_url_parser.cc.
         (FAVICON_URL_REGEX.test(url) ? 'iconurl/' : '') + url);
   }
 
   return {
+    getSupportedScaleFactors: getSupportedScaleFactors,
     getProfileAvatarIcon: getProfileAvatarIcon,
     getFaviconImageSet: getFaviconImageSet,
   };
 });