gecko-dev/editor/composer/crashtests/428844-1.html

<html class="reftest-wait">
<head>
<script>
function boom() {
  var iframe = document.getElementById('inner');
  iframe.addEventListener("load", function() {
    document.documentElement.removeAttribute("class");
  }, false);
  iframe.src = "data:text/html,";
  dump("Outer onload\n");
}
</script>
</head>
<body onload="boom()">
<iframe src="428844-1-inner.xhtml" id="inner"></iframe>
</body>
</html>