Host Chrome OS GAIA signin page in webview

chrome/browser/resources/chromeos/login/screen_gaia_signin.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.
  */
 
 #gaia-signin {
   height: 609px; /* Should be the same as #user-image.loading min-heigth. */
   padding: 70px 17px 69px;    /* Screen has no controls. */
   width: 722px; /* Should be the same as #user-image.loading width. */
 }
@@ skipping 71 matching lines @@
   display: none;
 }
 
 #signin-frame {
   background-color: transparent;
   margin-left: -44px;
   vertical-align: top;
   width: 400px;
 }
 
+webview#signin-frame {
+  display: block;
+  overflow: hidden;
+  padding: 0;
+}
+
 /* Simpler alignment if no right panel. */
 .no-right-panel #signin-frame {
   margin-left: 0;
 }
 
 /* Position to be aligned with the login box in iframe  */
 #login-box {
   height: 31px;
   position: absolute;
   top: 77px;
@@ skipping 47 matching lines @@
   left: 0;
   position: absolute;
   right: 0;
   text-align: center;
   top: 50px;
 }
 
 #saml-notice-message {
   margin: 0 auto;
 }