[Webapp Refactor] Implements remoting.Activity.

remoting/webapp/crd/js/activity.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.
+
+/** @suppress {duplicate} */
+var remoting = remoting || {};
+
+(function() {
+
+'use strict';
+
+/**
+ * An Activity is a responsible for
+ * 1. Showing the appropriate UX to establish a connection with the host and
+ *    create a remoting.ClientSession.
+ * 2. Handling connection failures and retrying if necessary.
+ * 3. Responding to session state changes and showing UX if necessary.
+ *
+ * @interface
+ * @extends {base.Disposable}
+ * @extends {remoting.ClientSession.EventHandler}
+ */
+remoting.Activity = function() {};
+
+/**
+ * Starts a new connection.
+ *
+ * @return {void}
+ */
+remoting.Activity.prototype.start = function() {};
+
+})();