Add support for favicon scale factor in WebUI

chrome/browser/resources/options/options_page.css

 /* 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. */
 
 body {
   position: relative;
 }
 
 #main-content {
   bottom: 0;
@@ skipping 351 matching lines @@
 }
 
 html[dir=rtl].option-name {
   padding-left: 5px;
 }
 
 .favicon-cell {
   -webkit-padding-start: 20px;
   background-position: left;
   background-repeat: no-repeat;
+  background-size: 16px;
 }
 
 input[type='url'].favicon-cell {
   -webkit-padding-start: 22px;
   background-position-x: 4px;
 }
 
 /* TODO(jhawkins): Use something better than 99.3% when CSS3 background
  * positioning is available.
  */
@@ skipping 193 matching lines @@
   background-size: 22px;
 }
 
 html[dir='rtl'] .controlled-setting-bubble-text {
   background-position: right top;
 }
 
 .controlled-setting-bubble-action {
   padding: 0 !important;
 }