[ChromeOS] Fix WebUI OOBE/Login background gradient.

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

Index: chrome/browser/resources/chromeos/login/oobe.css
diff --git a/chrome/browser/resources/chromeos/login/oobe.css b/chrome/browser/resources/chromeos/login/oobe.css
index 6c9f70f62255743d1f1965e305ad51b13b6bbbc2..29aeb6196de425443d232aed87d5bed049d4ebf2 100644
--- a/chrome/browser/resources/chromeos/login/oobe.css
+++ b/chrome/browser/resources/chromeos/login/oobe.css
@@ -5,9 +5,15 @@
  * 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;