<html>
  <head>
    <style></style>
    <script>
      o1 = document.createElement('t');
      document.documentElement.appendChild(o1);
      document.styleSheets[0].insertRule('* { will-change:an }', 0);
      k = new KeyframeEffect(o1, [{'willChange':'s'}], {'':''});
      k = null;
      SpecialPowers.forceGC();
      SpecialPowers.forceCC();
    </script>
  </head>
</html>
