Make the Most Visited tile focus state more apparent to match the online NTP.

chrome/browser/resources/local_ntp/local_ntp.css

 /* Copyright 2013 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 {
   background-attachment: fixed !important;
   background-color: white;
   cursor: default;
   font-family: arial, sans-serif;
   margin: 0;
   overflow-x: hidden;
@@ skipping 224 matching lines @@
   border: 1px solid #c0c0c0;
   cursor: pointer;
   outline: none;
 }
 
 .mv-page-ready:hover,
 .mv-page-ready:focus {
   border-color: #7f7f7f
 }
 
-.mv-thumb {
+.mv-thumb,
+.mv-mask {
   border: none;
   cursor: pointer;
   height: 83px;
   left: 0;
   position: absolute;
   top: 0;
   width: 138px;
 }
 
 .mv-title {
   border: none;
   bottom: -28px;
   height: 18px;
   left: 0;
   position: absolute;
   width: 140px;
 }
 
+.mv-mask {
+  opacity: 0.35;
+}
+
+.mv-page:focus .mv-mask {
+  -webkit-transition: background-color 100ms ease-in-out;
+  background: -webkit-linear-gradient(rgba(255, 255, 255, 0),
+    rgba(255, 255, 255, 0) 80%, rgba(255, 255, 255, 0.9));
+  background-color: black;
+}
+
 .mv-x-hide .mv-x {
   display: none;
 }
 
 /* An X button to blacklist a tile or hide the notification. */
 .mv-x {
   background: transparent url(images/close_2.png);
   border: none;
   cursor: default;
   height: 16px;
@@ skipping 144 matching lines @@
   -webkit-user-select: none;
   border: none;
   height: 22px;
   overflow: hidden;
   position: absolute;
 }
 
 #pending-suggestions-container {
   display: none;
 }