Fix supervised user dialog close regression.

chrome/browser/resources/options/supervised_user_learn_more.js

 // Copyright 2014 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.
 
 cr.define('options', function() {
   var Page = cr.ui.pageManager.Page;
 
   /**
    * SupervisedUserLearnMore class.
    * Encapsulated handling of the 'Learn more...' overlay page.
@@ skipping 10 matching lines @@
 
   SupervisedUserLearnMoreOverlay.prototype = {
     // Inherit from Page.
     __proto__: Page.prototype,
 
     /** @override */
     initializePage: function() {
       Page.prototype.initializePage.call(this);
 
       $('supervised-user-learn-more-done').onclick = function(event) {
-        Page.closeOverlay();
+        cr.ui.pageManager.PageManager.closeOverlay();
       };
     },
   };
 
   // Export
   return {
     SupervisedUserLearnMoreOverlay: SupervisedUserLearnMoreOverlay,
   };
 });