layout/reftests/css-transitions/style-change-during-transition.html

<!DOCTYPE html>
<html class="reftest-wait">
<style>
.container {
  visibility: visible;
  transition: visibility .2s;
}

.hidden {
  visibility: hidden;
}
</style>
<div id="tooltip" class="container hidden">
  <div>
    <div>
      <strong>Text</strong>
    </div>
  </div>
</div>
<script>
window.addEventListener("load", () => {
  requestIdleCallback(() => {
    tooltip.classList.remove("hidden");
    requestAnimationFrame(() => {
      requestAnimationFrame(() => {
        tooltip.style.zIndex = 2;
        document.documentElement.classList.remove("reftest-wait");
      });
    });
  });
});
</script>