[cros] Remove gray rectangle for focused user.

chrome/browser/resources/chromeos/login/user_pod_row.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.
  *
  * This is the stylesheet used by user pods row of account picker UI.
  */
 
 podrow {
   -webkit-box-align: center;
   -webkit-box-pack: center;
@@ skipping 21 matching lines @@
   background-color: #fff;
   border: 1px solid #ccc;
   border-radius: 2px;
   height: 160px;
   margin-bottom: 10px;
   padding: 4px;
   width: 160px;
 }
 
 .pod.focused {
-  background-color: #ebebeb;
   cursor: default;
 }
 
 .pod.faded {
   opacity: .75;
 }
 
 .pod.focused .user-image {
   -webkit-box-shadow: 0 6px 16px #a4a4a4;
   -webkit-transform: translateY(-1px);
@@ skipping 167 matching lines @@
   position: absolute;
   /* Width of .user-image. */
   width: 160px;
   z-index: 1;
 }
 
 .pod.focused .signed-in-indicator {
   /* Track shifting of .user-image on pod focus. */
   -webkit-transform: translateY(-1px);
 }