The Tor Browser / file revision

 /**

  * Any copyright is dedicated to the Public Domain.

  * http://creativecommons.org/publicdomain/zero/1.0/

  */

 onmessage = function(event) {

   var n = parseInt(event.data);

   if (n < 2) {

     postMessage(n);

     return;

   }

   var results = [];

   for (var i = 1; i <= 2; i++) {

     var worker = new Worker("fibonacci_worker.js");

     worker.onmessage = function(event) {

       results.push(parseInt(event.data));

       if (results.length == 2) {

         postMessage(results[0] + results[1]);

       }

     };

     worker.postMessage(n - i);

   }

 }