[Md Feedback] Add initial data population for dialog.

chrome/browser/resources/md_feedback/feedback.js

+// Copyright 2016 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.
+
+var Feedback = {};
+
+/**
+ * API invoked by the browser MdFeedbackWebUIMessageHandler to communicate
+ * with this UI.
+ */
+Feedback.UI = class {
+
+  /**
+   * Populates the feedback form with data.
+   *
+   * @param {{email: string|undefined,
+   *          url: string|undefined}} data
+   * Parameters in data:
+   *   email - user's email, if available.
+   *   url - url of the tab the user was on before triggering feedback.
+   */
+  static setData(data) {
+    $('container').email = data['email'];
+    $('container').url = data['url'];
+  }
+};
+
+/** API invoked by this UI to communicate with the browser WebUI message
+ * handler.
+ */
+Feedback.BrowserApi = class {
+  /**
+   * Requests data to initialize the WebUI with.
+   * The data will be returned via Feedback.UI.setData.
+   */
+  static requestData() {
+    chrome.send('requestData');
+  }
+};
+
+window.addEventListener('DOMContentLoaded', function() {
+  Feedback.BrowserApi.requestData();
+});