chromium/content/test/data/accessibility/css/display-to-block.html

<!--
@WAIT-FOR:done
@BLINK-ALLOW:display*
-->
<div>
  <div>Cats</div>
  <div id="block" style="display:none;">
      <input type="checkbox" aria-label="checkbox">
  </div>
  <div><code>pending</code></div>
</div>

<script>
  setTimeout(()=> {
    document.getElementById('block').style.display = 'block';
    document.querySelector('code').innerText = 'done';
  }, 100);
</script>