Add initial implementation of date-time-settings MD settings page.

chrome/browser/resources/settings/date_time_page/demo.js

 // Copyright 2015 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.
 
-// Wire up the prefs to the downloads page.
+// Wire up the prefs to the date/time page.
 window.addEventListener('polymer-ready', function() {
-  var page = document.querySelector('cr-settings-downloads-page');
+  var page = document.querySelector('cr-settings-date-time-page');
   page.prefs = document.querySelector('cr-settings-prefs');
 });