Add support for favicon scale factor in WebUI

chrome/browser/resources/options/search_engine_manager.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. */
 
 #search-engine-manager-page {
   width: 700px;
 }
 
 .search-engine-list input {
   -webkit-box-flex: 1;
   display: -webkit-box;
 }
 
 .search-engine-list > div {
   display: -webkit-box;
 }
 
 .search-engine-list .favicon {
+  background-position: center center;
+  background-repeat: no-repeat;
+  background-size: 16px;
   height: 16px;
   line-height: 16px;
   padding: 0 7px;
   width: 16px;
 }
 
 .search-engine-list .name-column {
   -webkit-box-align: center;
   -webkit-padding-end: 1ex;
   box-sizing: border-box;
@@ skipping 40 matching lines @@
   margin-top: 0;
   padding: 1px 6px 2px 6px;
 }
 
 .search-engine-list > :not(:hover):not([editing]) .url-column
     .list-inline-button {
   display: none;
 }
 
 /* End temporary Make Default button styling */