first-letter-inside-before-pseudo.html

<!DOCTYPE html>
  <link rel="author" title="Chris Harrelson" href="mailto:[email protected]">
  <meta name="assert" content="Test that the browser doesn't crash when a first-letter pseudo-element toggles visiblity as a child of a before pseudo-element.">
<style>
  .btn-text::before {
    content: "a";
    visibility: hidden;
  }

  .btn-text.visible::before {
    visibility: visible;
  }

  #problem::first-letter {
    text-transform: none;
  }
</style>
<div id="problem">
  <span class="btn-text"></span>
</div>
<script>
  requestAnimationFrame(() => requestAnimationFrame(() => {
    document.querySelector('.btn-text').classList.toggle('visible')
  }));
</script>

chromium/third_party/blink/web_tests/external/wpt/accessibility/crashtests/first-letter-inside-before-pseudo.html