<!DOCTYPE html>
<html class=reftest-wait>
<style>
.x .y { background-color: red; }
</style>
<p class=x><span><i class=y>hello</i></span></p>
<script>
addEventListener("MozReftestInvalidate", function() {
  document.querySelector("p").classList.toggle("x");
  document.querySelector("i").classList.toggle("y");
  document.documentElement.className = "";
}, false);
</script>