<!DOCTYPE HTML>
<html class="reftest-wait">
<head>
<script>
function doTest() {
  var d = document.getElementById("d");
  d.style.opacity = 0.5;
  document.documentElement.removeAttribute("class");
}
window.addEventListener("MozReftestInvalidate", doTest);
</script>
</head>
<body>
<div id="d" style="width:100px; height:100px; background:blue;">Hello</div>
</body>
</html>