[ChromeOS] Fix WebUI OOBE/Login background gradient.

Make html/body box occupy all available space so that the radial gradient show up correctly.

BUG=chromium-os:18866
TEST=Verify fix for chromium-os:18866.


Review URL: http://codereview.chromium.org/7599014

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@95958 0039d316-1c4b-4281-b951-d872f2087c98

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;