Add support for favicon scale factor in WebUI

chrome/browser/resources/options/browser_options_startup_page_list.js

 // Copyright (c) 2012 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('options.browser_options', function() {
   /** @const */ var AutocompleteList = cr.ui.AutocompleteList;
   /** @const */ var InlineEditableItem = options.InlineEditableItem;
   /** @const */ var InlineEditableItemList = options.InlineEditableItemList;
 
   /**
@@ skipping 39 matching lines @@
         pageInfo.title = loadTimeData.getString('startupAddLabel');
         pageInfo.url = '';
       }
 
       var titleEl = this.ownerDocument.createElement('div');
       titleEl.className = 'title';
       titleEl.classList.add('favicon-cell');
       titleEl.classList.add('weakrtl');
       titleEl.textContent = pageInfo.title;
       if (!this.isPlaceholder) {
-        titleEl.style.backgroundImage = url('chrome://favicon/' + pageInfo.url);
+        titleEl.style.backgroundImage = url('chrome://favicon/size/16@' +
+                                            window.devicePixelRatio + 'x/' +
+                                            pageInfo.url);
         titleEl.title = pageInfo.tooltip;
       }
 
       this.contentElement.appendChild(titleEl);
 
       var urlEl = this.createEditableTextCell(pageInfo.url);
       urlEl.className = 'url';
       urlEl.classList.add('weakrtl');
       this.contentElement.appendChild(urlEl);
 
@@ skipping 229 matching lines @@
       this.hideDropMarkerTimer_ = window.setTimeout(function() {
         $('startupPagesListDropmarker').style.display = '';
       }, 100);
     },
   };
 
   return {
     StartupPageList: StartupPageList
   };
 });