<!DOCTYPE html>
<html class="reftest-wait">
<iframe id="iframe" src="about:blank"></iframe>
<script>
iframe.onload = function() {
  let doc = iframe.contentDocument;
  let canvas = doc.createElement('canvas');
  doc.body.appendChild(canvas);
  let ctx = canvas.getContext('2d');
  document.body.offsetTop;
  iframe.style.display = 'none';
  try {
    ctx.font = '10px serif';
  } finally {
    document.documentElement.className = "";
  }
};
</script>
</html>
