Add basic versioning check to Chromoting's plugin/JS code.

remoting/webapp/me2mom/remoting_session.js

 // Copyright (c) 2011 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.
 
 // Maximum numer of lines to record in the debug log.
 // Only the most recent <n> lines are displayed.
 var MAX_DEBUG_LOG_SIZE = 1000;
+
 var remoting = chrome.extension.getBackgroundPage().remoting;
 
+// Chromoting session API version (for this javascript).
+// This is compared with the plugin API version to verify that they are
+// compatible.
+remoting.apiVersion = 1;
+
+// The oldest API version that we support.
+// This will differ from the |apiVersion| if we maintain backward
+// compatibility with older API versions.
+remoting.apiMinVersion = 1;
+
 // Message id so that we can identify (and ignore) message fade operations for
 // old messages.  This starts at 1 and is incremented for each new message.
 remoting.messageId = 1;
 
 remoting.scaleToFit = false;
 
 // Default to trying to sandboxed connections.
 remoting.connectMethod = 'sandboxed';
 remoting.httpXmppProxy =
     'https://chromoting-httpxmpp-oauth2-dev.corp.google.com';
@@ skipping 68 matching lines @@
   var xhr = new XMLHttpRequest();
   xhr.open('POST', remoting.httpXmppProxy + '/sendIq', true);
   xhr.withCredentials = true;
   xhr.setRequestHeader('Content-Type', 'application/x-www-form-urlencoded');
   xhr.send('to=' + encodeURIComponent(to) +
            '&payload_xml=' + encodeURIComponent(payload_xml) +
            '&id=' + id + '&type=' + type +
            '&host_jid=' + encodeURIComponent(remoting.hostjid));
 }
 
+function checkVersion(plugin) {
+  return remoting.apiVersion >= plugin.apiMinVersion &&
+      plugin.apiVersion >= remoting.apiMinVersion;
+}
+
 function init() {
   // Kick off the connection.
   var plugin = document.getElementById('remoting');
 
   remoting.plugin = plugin;
 
   // Only allow https connections to the httpXmppProxy.
   if (remoting.httpXmppProxy.search(/^ *https:\/\//) == -1) {
     addToDebugLog('Aborting. httpXmppProxy does not specify https protocol: ' +
                   remoting.httpXmppProxy);
     return;
   }
 
   // Setup the callback that the plugin will call when the connection status
   // has changes and the UI needs to be updated. It needs to be an object with
   // a 'callback' property that contains the callback function.
   plugin.connectionInfoUpdate = connectionInfoUpdateCallback;
   plugin.debugInfo = debugInfoCallback;
   plugin.desktopSizeUpdate = desktopSizeChanged;
   plugin.loginChallenge = loginChallengeCallback;
 
+  if (!checkVersion(plugin)) {
+    // TODO(garykac): We need better messaging here. Perhaps an install link.
+    setClientStateMessage("Out of date. Please re-install.");
+    return;
+  }
+
   addToDebugLog('Connect as user ' + remoting.username);
 
   // TODO(garykac): Clean exit if |connect| isn't a function.
   if (typeof plugin.connect === 'function') {
     if (remoting.connectMethod == 'sandboxed') {
       registerConnection();
     } else {
       plugin.connect(remoting.username, remoting.hostjid,
                      remoting.xmppAuthToken, remoting.accessCode);
     }
@@ skipping 181 matching lines @@
   setClientStateMessage(
       'Video stats: bandwidth: ' + videoBandwidth.toFixed(2) + 'Kbps' +
       ', Latency: capture: ' + videoCaptureLatency.toFixed(2) + 'ms' +
       ', encode: ' + videoEncodeLatency.toFixed(2) + 'ms' +
       ', decode: ' + videoDecodeLatency.toFixed(2) + 'ms' +
       ', render: ' + videoRenderLatency.toFixed(2) + 'ms');
 
   // Update the stats once per second.
   window.setTimeout('updateStatusBarStats()', 1000);
 }