[cros] check for updates in WebUI OOBE can be cancelled in dev builds.

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 260 matching lines @@
 
 #oobe.eula + #security-info {
   visibility: visible;
 }
 
 #update div {
   margin: 6em auto;
   width: 32em;
 }
 
+#update #update-cancel-hint {
+  color: #a00;
+  left: 50%;
+  margin: 1em -16em;
+  position: absolute;
+}
+
 #update progress {
   margin: 13px 0;
   width: 380px;
 }
 
 button {
   min-width: 80px;
 }
 
 .eula-columns {
@@ skipping 476 matching lines @@
 }
 
 .dropdown-overlay {
   bottom: 0;
   left: 0;
   position: fixed;
   right: 0;
   top: 0;
   z-index: 5;
 }