Implement bump-scroll browser-test.

remoting/webapp/js_proto/dom_proto.js

 // Copyright (c) 2012 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.
 
 // This file contains various hacks needed to inform JSCompiler of various
 // WebKit- and Chrome-specific properties and methods. It is used only with
 // JSCompiler to verify the type-correctness of our code.
 
 /** @type {HTMLElement} */
 Document.prototype.activeElement;
@@ skipping 201 matching lines @@
  * @param {*=} reason
  * @return {Promise}
  */
 Promise.reject = function (reason) {};
 
 /**
  * @param {*=} value
  * @return {Promise}
  */
 Promise.resolve = function (value) {};
+
+/**
+ * @param {string} type
+ * @param {boolean} canBubble
+ * @param {boolean} cancelable
+ * @param {Window} view
+ * @param {number} detail
+ * @param {number} screenX
+ * @param {number} screenY
+ * @param {number} clientX
+ * @param {number} clientY
+ * @param {boolean} ctrlKey
+ * @param {boolean} altKey
+ * @param {boolean} shiftKey
+ * @param {boolean} metaKey
+ * @param {number} button
+ * @param {EventTarget} relatedTarget
+ */
+Event.prototype.initMouseEvent = function(
+    type, canBubble, cancelable, view, detail,
+    screenX, screenY, clientX, clientY,
+    ctrlKey, altKey, shiftKey, metaKey,
+    button, relatedTarget) {};