Demo UI made with a help of WUG toolkit (DO NOT SEND TO CQ).

chrome/browser/resources/demo_ui/demo-element.js

Index: chrome/browser/resources/demo_ui/demo-element.js
diff --git a/chrome/browser/resources/demo_ui/demo-element.js b/chrome/browser/resources/demo_ui/demo-element.js
new file mode 100644
index 0000000000000000000000000000000000000000..968da994a87f306c0d0265a62c647eba94b3b00f
--- /dev/null
+++ b/chrome/browser/resources/demo_ui/demo-element.js
@@ -0,0 +1,19 @@
+// 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.
+
+Polymer('demo-element', {
+  selectedPage: 0,
+  contextDump: null,
+
+  initialize: function() {
+    this.contextChanged();
+  },
+
+  contextChanged: function(changedKeys) {
+    this.contextDump = [];
+    for (var key in this.C) {
+      this.contextDump.push({ 'key': key, 'value': this.C[key].toString() });
+    }
+  }
+});