shadow-tree-listener-clearance-frame.html

<!DOCTYPE html>
<html>
<body>
<div id="host"></div>
<script>
(function() {
    var shadow = document.getElementById("host").attachShadow({mode: 'open'});
    shadow.innerHTML = "<article id='target'></article>";
    document.targetInShadow = shadow.getElementById("target");
})();
</script>
</body>
</html>

chromium/third_party/blink/web_tests/fast/dom/shadow/resources/shadow-tree-listener-clearance-frame.html