layout-slot-no-longer-fallback.html

<!DOCTYPE html>
<title>Layout using slot elements</title>
<link rel="author" title="Hayato Ito" href="mailto:[email protected]"/>
<link rel="help" href="https://dom.spec.whatwg.org/#shadow-tree-slots">
<link rel="match" href="reference/empty.html"/>
<div id="host"></div>
<script>
const host = document.querySelector('#host');
const sr = host.attachShadow({ mode: 'open' });

sr.innerHTML = '<slot><div id="fallback">Should not be displayed</div></slot>'

document.body.offsetLeft;
host.appendChild(document.createElement('div'));
</script>

chromium/third_party/blink/web_tests/external/wpt/shadow-dom/layout-slot-no-longer-fallback.html