DevTools: introduce a stub for the new audits panel (behind experiment).

third_party/WebKit/Source/devtools/front_end/audits2_worker/Audits2Service.js

+// Copyright (c) 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.
+
+/**
+ * @constructor
+ * @implements {Service}
+ */
+function Audits2Service()
+{
+}
+
+Audits2Service.prototype = {
+    /**
+     * @return {!Promise}
+     */
+    start: function()
+    {
+        console.error("WORKER START");
+        return Promise.resolve();
+    },
+
+    /**
+     * @return {!Promise}
+     */
+    stop: function()
+    {
+        console.error("WORKER STOP");
+        return Promise.resolve();
+    },
+
+    /**
+     * @override
+     */
+    dispose: function()
+    {
+        console.error("WORKER DISPOSE");
+    }
+}
+
+initializeWorkerService("Audits2Service", Audits2Service);