chromium/content/test/data/accessibility/display-locking/selectmenu.html

<!DOCTYPE html>
<selectmenu></selectmenu>
<div></div>

<script>
  (async () => {
    const selectmenu = document.querySelector('selectmenu');
    await getComputedAccessibleNode(document.querySelector('div'));
    selectmenu.style.setProperty('content-visibility', 'hidden');
  })();
</script>