Options: Remove the hidden class, since we override the hidden attribute to set

chrome/browser/resources/options/browser_options.js

 // Copyright (c) 2011 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() {
   const OptionsPage = options.OptionsPage;
   const ArrayDataModel = cr.ui.ArrayDataModel;
 
   //
   // BrowserOptions class
@@ skipping 110 matching lines @@
         };
       }
 
       var startupPagesList = $('startupPagesList');
       options.browser_options.StartupPageList.decorate(startupPagesList);
       startupPagesList.autoExpands = true;
 
       // Check if we are in the guest mode.
       if (cr.commandLine.options['--bwsi']) {
         // Hide the startup section.
-        $('startupSection').classList.add('hidden');
+        $('startupSection').hidden = true;
       } else {
         // Initialize control enabled states.
         Preferences.getInstance().addEventListener('session.restore_on_startup',
             this.updateCustomStartupPageControlStates_.bind(this));
         Preferences.getInstance().addEventListener(
             this.startup_pages_pref_.name,
             this.handleStartupPageListChange_.bind(this));
         Preferences.getInstance().addEventListener(
             this.homepage_pref_.name,
             this.handleHomepageChange_.bind(this));
@@ skipping 336 matching lines @@
   BrowserOptions.updateAutocompleteSuggestions = function(suggestions) {
     BrowserOptions.getInstance().updateAutocompleteSuggestions_(suggestions);
   };
 
   // Export
   return {
     BrowserOptions: BrowserOptions
   };
 
 });