The Tor Browser / file revision

 function run_test() {

   var ioService = Components.classes["@mozilla.org/network/io-service;1"]

                             .getService(Components.interfaces.nsIIOService);

   try {

     var linkService = Components.classes["@mozilla.org/network/network-link-service;1"]

                                 .getService(Components.interfaces.nsINetworkLinkService);

     // The offline status should depends on the link status

     do_check_neq(ioService.offline, linkService.isLinkUp);

   } catch (e) {

     // The network link service might not be available

     do_check_eq(ioService.offline, false);

   }

 }