Revert of Remove NPAPI plugin from chromoting webapp.

remoting/webapp/host_session.js

 // Copyright (c) 2012 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.
 
 /**
  * @fileoverview
  * Class handling creation and teardown of a remoting host session.
  *
  * This abstracts a <embed> element and controls the plugin which does the
  * actual remoting work.  There should be no UI code inside this class.  It
@@ skipping 97 matching lines @@
   return this.hostDispatcher_.getClient();
 };
 
 /**
  * Disconnect the it2me session.
  * @return {void} Nothing.
  */
 remoting.HostSession.prototype.disconnect = function() {
   this.hostDispatcher_.disconnect();
 };
+
+
+/**
+ * @return {void} Nothing.
+ */
+remoting.HostSession.prototype.cleanup = function() {
+  this.hostDispatcher_.cleanup();
+};