The Tor Browser / file revision

 this.EXPORTED_SYMBOLS = ['checkFromJSM'];

 this.checkFromJSM = function checkFromJSM(ok, is) {

   Components.utils.importGlobalProperties(['URL']);

   var url = new URL('http://www.example.com');

   is(url.href, "http://www.example.com/", "JSM should have URL");

   var url2 = new URL('/foobar', url);

   is(url2.href, "http://www.example.com/foobar", "JSM should have URL - based on another URL");

   var blob = new Blob(['a']);

   var url = URL.createObjectURL(blob);

   ok(url, "URL is created!");

   URL.revokeObjectURL(url);

   ok(true, "URL is revoked");

 }