[cros] Hide user pods on Login screen while images are loading.

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;
   display: -webkit-box;
   position: relative;
 }
 
+/* Hide the pod row while images are loading. */
+podrow.images-loading {
+  visibility: hidden;
+}
+
 html[oobe=old] podrow {
   height: 230px;
 }
 
 .pod {
   border-radius: 2px;
   cursor: pointer;
   outline: none;
   padding: 10px;
   position: relative;
@@ skipping 268 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;
 }