LayoutTests/webanimations/css-animation-resolution-during-teardown.html

<style>
  @keyframes a0 {
  }
  div, span {
    animation-name: a0;
  }
  slot {
    animation-name: a0, a0;
  }
</style>
<script>
  window.testRunner?.dumpAsText();
  window.testRunner?.waitUntilDone();

  onload = () => {
    document.body.append(document.createElement('input'));
    document.body.append(document.createElement('slot'));
    let br0 = document.createElement('br');
    document.body.append(br0);
    let div0 = document.createElement('div');
    br0.append(div0);
    document.body.offsetTop;
    document.body.append(document.createElement('input'));
    div0.append(document.createElement('span'));
    document.execCommand('SelectAll');
    onbeforeunload = () => {
      document.styleSheets[0].insertRule(`slot { animation-delay: 25ms; }`);
      document.designMode = 'on';
      document.execCommand('Bold');
    };

    requestAnimationFrame(() => {
        if (!window.location.search)
            window.location.href = window.location.href + "?foo=1";
        else {
            document.body.textContent = "PASS";
            window.testRunner?.notifyDone();
        }
    });
  };
</script>