[cros] Initialize OOBE in parallel when boot animation is disabled.

chrome/browser/resources/chromeos/login/user_pod_row.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.
  *
  * This is the stylesheet used by user pods row of account picker UI.
  */
 
 podrow {
   -webkit-box-align: center;
   -webkit-box-pack: center;
+  /* -webkit-transition: all 180ms linear; */
   display: -webkit-box;
+  /* opacity: 1; */
   position: relative;
 }
 
 /* Hide the pod row while images are loading. */
 podrow.images-loading {
+  /* opacity: 0; */
   visibility: hidden;
 }
 
 html[oobe=old] podrow {
   height: 230px;
 }
 
 .pod {
   border-radius: 2px;
   cursor: pointer;
@@ skipping 278 matching lines @@
 
 html[oobe=old] .signed-in-indicator {
   margin: 5px;
 }
 
 html[oobe=old] .pod.focused .signed-in-indicator {
   /* Track shifting of .user-image on pod focus. */
   -webkit-transform: translateY(-1px);
   -webkit-transition: -webkit-transform 140ms ease;
 }