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

third_party/WebKit/Source/devtools/front_end/audits2/Audits2Panel.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
+ * @extends {WebInspector.Panel}
+ */
+WebInspector.Audits2Panel = function()
+{
+    WebInspector.Panel.call(this, "audits2");
+    this.contentElement.classList.add("vbox");
+    this.contentElement.appendChild(createTextButton(WebInspector.UIString("Start"), this._start.bind(this)));
+    this.contentElement.appendChild(createTextButton(WebInspector.UIString("Stop"), this._stop.bind(this)));
+}
+
+WebInspector.Audits2Panel.prototype = {
+    _start: function()
+    {
+        this._backend().then(backend => backend ? backend.send("start") : undefined).then(console.error.bind(console, "STARTED"));
+    },
+
+    _stop: function()
+    {
+        this._backend().then(backend => backend ? backend.send("stop") : undefined).then(console.error.bind(console, "STOPPED"));
+    },
+
+    /**
+     * @return {!Promise<?WebInspector.ServiceManager.Service>}
+     */
+    _backend: function()
+    {
+        if (!this._backendPromise)
+            this._backendPromise = WebInspector.serviceManager.createAppService("audits2_worker", "Audits2Service", false);
+        return this._backendPromise;
+    },
+
+    __proto__: WebInspector.Panel.prototype
+}