The Tor Browser / file revision

 var Ci = Components.interfaces;

 var Cc = Components.classes;

 var nativeJSON = Cc["@mozilla.org/dom/json;1"].createInstance(Ci.nsIJSON);

 function run_test()

 {

   function read_file(path)

   {

     try

     {

       var f = do_get_file(path);

       var istream = Cc["@mozilla.org/network/file-input-stream;1"].createInstance(Ci.nsIFileInputStream);

       istream.init(f, -1, -1, false);

       return nativeJSON.decodeFromStream(istream, istream.available());

     }

     finally

     {

       istream.close();

     }

   }

   var x = read_file("decodeFromStream-01.json");

   do_check_eq(x["JSON Test Pattern pass3"]["The outermost value"], "must be an object or array.");

   do_check_eq(x["JSON Test Pattern pass3"]["In this test"], "It is an object.");

   x = read_file("decodeFromStream-small.json");

   do_check_eq(x.toSource(), "({})", "empty object parsed");

 }