[ChromeOS] Fix WebUI OOBE/Login background gradient.

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%;
+  width: 100%;
+}
+
 body {
   background: -webkit-gradient(radial, center center, 0, center center, 400,
-              from(#fefefe), to(#efefef));
+              from(#fefefe), to(#efefef)) center center no-repeat;
   font-size: 14px;
   overflow: hidden;
   padding: 10px;
 }
 
 #oobe {
   left: 50%;
   margin-left: -320px;
   margin-top: -270px;
   position: absolute;
@@ skipping 623 matching lines @@
 #version-labels {
   -webkit-transition: all .5s linear;
   bottom: 10px;
   color: #999;
   font-size: 11px;
   left: 10px;
   opacity: 1.0;
   position: absolute;
   text-shadow: 0 1px 1px #fff;
 }