<!DOCTYPE html>
<html>
<head>
<meta charset="utf-8">
<title>Testcase for bug 643706 of Mozilla</title>
<script>
function boom() {
  const iframe = document.querySelector("iframe");
  const win = iframe.contentWindow;
  win.document.designMode = 'on';
  iframe.style.content = "'m'";
  win.document.removeChild(win.document.documentElement)
}
</script>
</head>
<body onload="boom();"><iframe srcdoc=""></iframe></body>
</html>
