Use PageManager in About page

chrome/browser/resources/options/options_settings_app.js

 // Copyright 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.
 
 (function() {
   if (document.location != 'chrome://settings-frame/options_settings_app.html')
     return;
 
   OptionsPage.setIsSettingsApp(true);
 
   // Override the offset in the options page.
-  PageManager.setHorizontalOffset(38);
+  PageManager.horizentalOffset = 38;
 
   document.addEventListener('DOMContentLoaded', function() {
     // Hide everything by default.
     var sections = document.querySelectorAll('section');
     for (var i = 0; i < sections.length; i++)
       sections[i].hidden = true;
 
     var whitelistedSections = [
       'advanced-settings',
       'downloads-section',
@@ skipping 19 matching lines @@
     $('profiles-create').hidden = true;
     $('profiles-delete').hidden = true;
     $('profiles-manage').hidden = true;
 
     // Remove the 'X'es on profiles in the profile list.
     $('profiles-list').canDeleteItems = false;
   });
 
   loadTimeData.overrideValues(loadTimeData.getValue('settingsApp'));
 }());