css/compositing/root-element-opacity-change.html

<!doctype HTML>
<html class="test-wait" style="font-size: 200px; opacity: 0.5">
<link rel="help" href="https://drafts.fxtf.org/compositing/#pagebackdrop">
<link rel="match" href="root-element-opacity-change-ref.html">
<meta name="assert" content="View background should be white after opacity changes from 0.5 to 1">
<script src="/common/rendering-utils.js"></script>
TEST
<script>
waitForAtLeastOneFrame().then(() => {
  document.documentElement.style.opacity=1;
  document.documentElement.classList.remove('test-wait');
});
</script>
</html>