<!--
  Any copyright is dedicated to the Public Domain.
  http://creativecommons.org/publicdomain/zero/1.0/
-->
<!DOCTYPE HTML>
<html>
<head>
  <meta charset="utf-8">
</head>
<body>
<script type="text/javascript">
  window.parent.postMessage({
    controlled: !!navigator.serviceWorker.controller
  }, "*");

  addEventListener("message", e => {
    if (e.data == "create nested iframe") {
      const iframe = document.createElement('iframe');
      document.body.appendChild(iframe);
      iframe.src = location.href;
    } else {
      window.parent.postMessage(e.data, "*");
    }
  });
</script>
</body>
</html>
