The updated (simplified) look of set-as-default dialog on Windows8.

chrome/browser/resources/set_as_default_browser.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.
 
 (function() {
   // Since all we want here is forwarding of certain commands, all can be done
   // in the anonymous function's scope.
 
   function wireUpWindow() {
     $('launch-button').addEventListener('click', function() {
       chrome.send('SetAsDefaultBrowser:LaunchSetDefaultBrowserFlow');
     });
-
-    $('return-button').addEventListener('click', function() {
-      chrome.send('SetAsDefaultBrowser:ReturnToBrowser');
-    });
   }
 
   window.addEventListener('DOMContentLoaded', wireUpWindow);
 })();