engagement_autoplay_iframe_delegation.html

<!DOCTYPE html>
<meta charset="utf-8">
<title>Media Engagement Test</title>
<iframe allow="autoplay" name="subframe" frameborder="0" style="width:500px;height:500px"></iframe>
<script>
window.addEventListener("message", function(e) {
  window.document.title = e.data;
}, false);
</script>

chromium/chrome/test/data/media/engagement/engagement_autoplay_iframe_delegation.html