Improve accessibility of user image selection screen.

chrome/browser/resources/options2/chromeos/change_picture_options.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. */
 
 #change-picture-page .content-area {
   min-width: 800px;
 }
 
 #user-image-grid {
   -webkit-user-drag: none;
@@ skipping 12 matching lines @@
   padding: 0;
 }
 
 #user-image-grid img {
   background-color: white;
   height: 64px;
   vertical-align: middle;
   width: 64px;
 }
 
-#user-image-grid [role=listitem] {
+#user-image-grid > li {
   border: 1px solid rgba(0, 0, 0, 0.15);
   border-radius: 4px;
   display: inline-block;
   margin: 8px;
   padding: 3px;
 }
 
 #user-image-grid [selected] {
   border: 2px solid rgb(0, 102, 204);
   padding: 2px;
@@ skipping 138 matching lines @@
 }
 
 #user-image-attribution {
   -webkit-padding-start: 34px;
   line-height: 26px;
 }
 
 #user-image-author-website {
   -webkit-padding-start: 5px;
 }