Add an initial implementation of the downloads MD settings page.

chrome/browser/resources/settings/downloads_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.

[michaelpg, 2015/03/08 05:37:36]

optional nit: I'm not sure this really need to be a JSDoc, as opposed to a
single // comment

[Kyle Horimoto, 2015/03/09 20:16:21]

Yep, I don't think this an appropriate JSDoc use case.

[Oren Blasberg, 2015/03/09 21:05:05]

Done.

+ */
+window.onload = function() {

[michaelpg, 2015/03/08 05:37:36]

Prefer window.addEventListener('polymer-ready', ...) to ensure that "page.prefs"
has been set up as a published property.

[Oren Blasberg, 2015/03/09 21:05:05]

Done.

+  var page = document.querySelector('cr-settings-downloads-page');
+  page.prefs = document.querySelector('cr-settings-prefs');
+};