Show error if plugin doesn't support PIN auth.

remoting/webapp/client_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 'client screen' for Chromoting.
  */
 
 'use strict';
@@ skipping 386 matching lines @@
       remoting.clientSession.state != remoting.ClientSession.State.CONNECTED) {
     return;
   }
   var stats = remoting.clientSession.stats();
   remoting.debug.updateStatistics(stats);
   remoting.clientSession.logStatistics(stats);
   // Update the stats once per second.
   window.setTimeout(updateStatistics_, 1000);
 }
 
+/**
+ * @return {boolean} true if the client plugin supports PIN auth.
+ */
+remoting.isPinAuthSupported = function () {
+  var plugin = /** @type {remoting.ViewerPlugin} */
+      document.createElement('embed');
+  plugin.src = 'about://none';
+  plugin.type = 'pepper-application/x-chromoting';
+  plugin.width = 0;
+  plugin.height = 0;
+  document.body.appendChild(plugin);
+  var version = plugin.apiVersion;
+  document.body.removeChild(plugin);
+  return version && version >= 4;
+};
 
 /**
  * Shows PIN entry screen.
  *
  * @param {string} hostId The unique id of the host.
  * @param {boolean} retryIfOffline If true and the host can't be contacted,
  *     refresh the host list and try again. This allows bookmarked hosts to
  *     work even if they reregister with Talk and get a different Jid.
  * @return {void} Nothing.
  */
 remoting.connectMe2Me = function(hostId, retryIfOffline) {
   remoting.currentConnectionType = remoting.ConnectionType.Me2Me;
   remoting.hostId = hostId;
   remoting.retryIfOffline = retryIfOffline;
 
-  // TODO(sergeyu): Ask pin only when it is necessary: crbug.com/111290 .
+  if (!remoting.isPinAuthSupported()) {
+    showConnectError_(remoting.Error.BAD_PLUGIN_VERSION);
+    return;
+  }
+
   remoting.setMode(remoting.AppMode.CLIENT_PIN_PROMPT);
 };
 
 /**
  * Start a connection to the specified host, using the cached details
  * and the PIN entered by the user.
  *
  * @return {void} Nothing.
  */
 remoting.connectMe2MeWithPin = function() {
@@ skipping 32 matching lines @@
             /** @type {string} */ (remoting.oauth2.getCachedEmail()),
             remoting.ClientSession.Mode.ME2ME, onClientStateChange_);
     remoting.clientSession.createPluginAndConnect(
         document.getElementById('session-mode'),
         token);
     remoting.setScaleToFit(remoting.clientSession.getScaleToFit());
   } else {
     showConnectError_(remoting.Error.AUTHENTICATION_FAILED);
   }
 }