Make the OOBE network menu accessible by improving keyboard handling

chrome/browser/resources/chromeos/login/oobe.css

 /* Copyright (c) 2011 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 the Out of the box experience (OOBE) flow.
  */
 
 html,
 body {
   height: 100%;
@@ skipping 207 matching lines @@
   margin: 5px 5px 5px 5px;
 }
 
 .menu-control {
   font-family: inherit;
   line-height: 20px;
   width: 250px;
 }
 
 .label {
+  display: block;
   margin: 5px 5px 5px 0;
   padding: 5px 5px 5px 0;
   width: 170px;
 }
 
 #connect {
   box-sizing: border-box;
   padding: 60px 0 0 145px;
 }
 
@@ skipping 442 matching lines @@
   left: 10px;
   opacity: 1.0;
   position: absolute;
   right: 10px;
   text-shadow: 0 1px 1px #fff;
 }
 
 #offline-network-control {
   margin-left: 60px;
 }