Revert of Remove NPAPI plugin from chromoting webapp.

remoting/webapp/host_screen.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
  * Functions related to the 'host screen' for Chromoting.
  */
 
 'use strict';
@@ skipping 15 matching lines @@
  * to install them if necessary.
  */
 remoting.tryShare = function() {
   /** @type {remoting.HostIt2MeDispatcher} */
   var hostDispatcher = new remoting.HostIt2MeDispatcher();
 
   /** @type {remoting.HostInstallDialog} */
   var hostInstallDialog = null;
 
   var tryInitializeDispatcher = function() {
-    hostDispatcher.initialize(onDispatcherInitialized,
+    hostDispatcher.initialize(createPluginForIt2Me,
+                              onDispatcherInitialized,
                               onDispatcherInitializationFailed);
   }
 
+  /** @return {remoting.HostPlugin} */
+  var createPluginForIt2Me = function() {
+    return remoting.createNpapiPlugin(
+        document.getElementById('host-plugin-container'));
+  }
+
   var onDispatcherInitialized = function () {
-    // Host already installed.
-    remoting.startHostUsingDispatcher_(hostDispatcher);
+    if (hostDispatcher.usingNpapi()) {
+      hostInstallDialog = new remoting.HostInstallDialog();
+      hostInstallDialog.show(tryInitializeDispatcher, onInstallError);
+    } else {
+      // Host alrady installed.
+      remoting.startHostUsingDispatcher_(hostDispatcher);
+    }
   };
 
   /** @param {remoting.Error} error */
   var onDispatcherInitializationFailed = function(error) {
     if (error != remoting.Error.MISSING_PLUGIN) {
       showShareError_(error);
       return;
     }
 
     // If we failed to initialize the dispatcher then prompt the user to install
@@ skipping 109 matching lines @@
     if (remoting.currentMode != remoting.AppMode.HOST_SHARE_FAILED) {
       // If an error is being displayed, then the plugin should not be able to
       // hide it by setting the state. Errors must be dismissed by the user
       // clicking OK, which puts the app into mode HOME.
       if (lastShareWasCancelled_) {
         remoting.setMode(remoting.AppMode.HOME);
       } else {
         remoting.setMode(remoting.AppMode.HOST_SHARE_FINISHED);
       }
     }
+    remoting.hostSession.cleanup();
+
   } else if (state == remoting.HostSession.State.ERROR) {
     console.error('Host state: ERROR');
     showShareError_(remoting.Error.UNEXPECTED);
   } else if (state == remoting.HostSession.State.INVALID_DOMAIN_ERROR) {
     console.error('Host state: INVALID_DOMAIN_ERROR');
     showShareError_(remoting.Error.INVALID_HOST_DOMAIN);
   } else {
     console.error('Unknown state -> ' + state);
   }
 }
@@ skipping 158 matching lines @@
  * @private
  */
 function onNatTraversalPolicyChanged_(enabled) {
   var natBox = document.getElementById('nat-box');
   if (enabled) {
     natBox.classList.add('traversal-enabled');
   } else {
     natBox.classList.remove('traversal-enabled');
   }
 }