Download the host components when user tries to enable Me2Me host.

remoting/webapp/host_controller.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.
 
 'use strict';
 
 /** @suppress {duplicate} */
 var remoting = remoting || {};
 
 /** @constructor */
 remoting.HostController = function() {
   /** @return {remoting.HostPlugin} */
   var createPluginForMe2Me = function() {
     var plugin = remoting.HostSession.createPlugin();
     /** @type {HTMLElement} @private */
     var container = document.getElementById('daemon-plugin-container');
     container.appendChild(plugin);
+    if (plugin.hasOwnProperty('REQUESTED_ACCESS_CODE')) {
+      container.removeChild(plugin);
+      return null;
+    }
     return plugin;
   };
 
   /** @type {remoting.HostDispatcher} @private */
   this.hostDispatcher_ = new remoting.HostDispatcher(createPluginForMe2Me);
 
   /** @param {string} version */
   var printVersion = function(version) {
     if (version == '') {
       console.log('Host not installed.');
@@ skipping 437 matching lines @@
  *
  * @param {function():void} onDone Completion callback.
  * @param {function(remoting.Error):void} onError Error callback.
  * @return {void}
  */
 remoting.HostController.prototype.clearPairedClients = function(
     onDone, onError) {
   this.hostDispatcher_.clearPairedClients(onDone, onError);
 };
 
+/**
+ * Returns true if the NPAPI plugin is being used.
+ * @return {boolean}
+ */
+remoting.HostController.prototype.usingNpapiPlugin = function() {
+  return this.hostDispatcher_.usingNpapiPlugin();
+}
+
 /** @type {remoting.HostController} */
 remoting.hostController = null;