<!DOCTYPE html>
<html class="reftest-wait">
<head>
<body>
<p id="first">f<span>o</span>o</p>
<p id="second">bar</p>
<script>
document.body.offsetTop;
var p1 = document.getElementById("first");
var p2 = document.getElementById("second");
var selection = window.getSelection();
selection.setBaseAndExtent(p1.firstChild, 0, p1.lastChild, 0);

function doTest() {
  selection.extend(p2.firstChild, 2);
  document.documentElement.removeAttribute('class');
}
document.addEventListener("MozReftestInvalidate", doTest);
</script>
</body>
</html>