<!DOCTYPE html>
<html class="reftest-wait">
  <body>
    <style>
      #a { border: 1px solid black; max-width: 100px; height: 100px; }
    </style>
    <script>
      document.addEventListener("MozReftestInvalidate", function() {
        var a = document.querySelector("#a");
        a.style.maxWidth = "200px";
        document.documentElement.removeAttribute("class");
      });
    </script>
    <div id="a">
    </div>
  </body>
</html>