[cros] OOBE slide animation.

chrome/browser/resources/chromeos/login/network_dropdown.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 the network drop-down control.
  */
 
 .dropdown-title {
   -webkit-appearance: none;
   -webkit-box-align: start;
@@ skipping 62 matching lines @@
 .dropdown-title div {
   -webkit-box-flex: 1;
   margin-top: 1px;
   overflow: hidden;
   text-overflow: ellipsis;
 }
 
 .dropdown-container {
   background: #f7f7f7;
   border: 1px solid rgb(124, 145, 191);
-  max-height: 330px;
+  max-height: 300px;
   overflow-x: hidden;
   overflow-y: auto;
   padding-bottom: 2px;
   padding-top: 2px;
   position: absolute;
   top: 100%;
   width: 99.5%;
   z-index: 10;
 }
 
@@ skipping 35 matching lines @@
 }
 
 .dropdown-overlay {
   bottom: 0;
   left: 0;
   position: fixed;
   right: 0;
   top: 0;
   z-index: 5;
 }
-