<html>
  <head>
    <script>
onload = function() {
  var x = null;
  try {
    x = document.createElementNS("http://www.mozilla.org/keymaster/gatekeeper/there.is.only.xul", "spacer");
  } catch(ex) {}
  window.parent.postMessage(x == null, "http://mochi.test:8888");
}
    </script>
  </head>
  <body>
    Here be dragons!
  </body>
</html>
