Add chrome://site-engagement WebUI.

chrome/browser/resources/engagement/engagement_table.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.
+
+'use strict';
+
+Polymer({
+  is: 'engagement-table',
+  properties: {
+    /**
+     * A list of engagement info objects.
+     * @type !Array<!SiteEngagementInfo>
+     */
+    engagementInfo: {
+      type: Array,
+      value: () => []

[Dan Beam, 2015/09/10 17:33:54]

though this is fine, be aware that if you ever need this code to run on iOS, it
may not work

[calamity, 2015/09/11 07:48:24]

Acknowledged.

+    },
+  },
+
+});