<!DOCTYPE html>
<script>
function runRaf(countdown) {
  countdown--;
  if (countdown > 0)
    requestAnimationFrame(function() { runRaf(countdown); });
}
requestAnimationFrame(function() { runRaf(5); });
requestAnimationFrame(function() { runRaf(10); });
</script>
<div>Main frame</div>
<iframe src="data:text/html,Test page"></iframe>