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