[Icons NTP] Make Fast Local NTP render largeIconUrl instead of thumbnail, if available.

chrome/browser/resources/local_ntp/most_visited_single.css

 /* Copyright 2015 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 {
   -webkit-user-select: none;
   background: none transparent;
   color: #323232;
   margin: 0;
   overflow: hidden;
@@ skipping 133 matching lines @@
   cursor: pointer;
   display: block;
   height: 94px;
   left: 3px;
   overflow: hidden;
   position: absolute;
   top: 31px;
   width: 148px;
 }
 
-.mv-thumb img {
+.mv-thumb img.thumbnail {
   height: auto;
   min-height: 100%;
   width: 100%;
 }
 
-.mv-thumb.failed-img {
+.mv-thumb img.large-icon {
+  height: 48px;
+  left: 50%;
+  margin-left: -24px;
+  margin-top: -24px;
+  position: absolute;
+  top: 50%;
+  width: 48px;
+}
+
+.mv-thumb.failed-img,
+.mv-thumb.large-icon-outer {
   background-color: #fff;
   height: 94px;
   width: 148px;
 }
 
 /*
   We use ::after without content to provide an aditional element on top of
   the thumbnail.
 */
 .mv-thumb.failed-img::after {
@@ skipping 82 matching lines @@
   background-image: -webkit-image-set(
       url(chrome-search://local-ntp/images/ntp_default_favicon.png) 1x,
       url(chrome-search://local-ntp/images/ntp_default_favicon.png@2x) 2x);
   background-repeat: no-repeat;
   background-size: 16px 16px;
 }
 
 .mv-favicon.failed-favicon img {
   display: none;
 }