cros: Fix header bar not showing up on lock screen.

chrome/browser/resources/chromeos/login/header_bar.js

 // 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.
 
 /**
  * @fileoverview Login UI header bar implementation.
  */
 
 cr.define('login', function() {
   /**
@@ skipping 208 matching lines @@
     /**
      * Animates Header bar to slowly appear on the screen.
      */
     animateIn: function() {
       this.classList.remove('login-header-bar-animate-fast');
       this.classList.add('login-header-bar-animate-slow');
       this.classList.remove('login-header-bar-hidden');
     },
   };
 
+  /**
+   * Convenience wrapper of animateOut.
+   */
+  HeaderBar.animateOut = function(callback) {
+    $('login-header-bar').animateOut(callback);
+  };
+
+  /**
+   * Convenience wrapper of animateIn.
+   */
+  HeaderBar.animateIn = function() {
+    $('login-header-bar').animateIn();
+  }
+
   return {
     HeaderBar: HeaderBar
   };
 });