[Chromoting] Enable jscompile for browser tests.

remoting/webapp/js_proto/test_proto.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.
+
+// This file contains various hacks needed to inform JSCompiler of various
+// test-specific properties and methods. It is used only with JSCompiler to
+// verify the type-correctness of our code.
+
+/** @suppress {duplicate} */
+var browserTest = browserTest || {};
+
+/** @suppress {duplicate} */
+var sinon = sinon || {};
+
+/** @interface */
+browserTest.TestableClass = function() {};
+
+/** @param {*} data */
+browserTest.TestableClass.prototype.run = function(data) {};
+
+sinon.spy = function() {};
+
+/** @constructor */
+window.DomAutomationControllerMessage = function() {
+  /** @type {boolean} */
+  this.succeeded = false;
+  /** @type {string} */
+  this.error_message = '';
+  /** @type {string} */
+  this.stack_trace = '';
+};
+
+/** @constructor */
+window.DomAutomationController = function() {};
+
+/** @param {string} json A stringified DomAutomationControllerMessage. */
+window.DomAutomationController.prototype.send = function(json) {};