[DevTools] Extract part of DevTools into inspector app.

Source/devtools/front_end/host/InspectorAppHost.js

+// Copyright 2014 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.
+
+/**
+ * @interface
+ */
+function InspectorAppHostAPI()
+{
+}
+
+InspectorAppHostAPI.prototype = {
+    /**
+     * @param {!Window} window
+     */
+    inspectorAppWindowLoaded: function(window) { },
+
+    beforeInspectorAppLoad: function() { },
+
+    afterInspectorAppLoad: function() { }
+}
+
+/**
+ * @type {!InspectorAppHostAPI}
+ */
+var InspectorAppHost;
+
+/**
+ * @suppressGlobalPropertiesCheck
+ */
+(function()
+{
+    if (window.parent !== window) {
+        InspectorAppHost = window.parent.InspectorAppHost;
+        InspectorAppHost.inspectorAppWindowLoaded(window);
+    }
+})();