<!DOCTYPE html>
<link rel="help" href="http://crbug.com/1146872">
<body>
<fieldset><span><span></span></span></fieldset>
<div id="host"><span></span></div>
<script>
const host = document.querySelector('#host');
const shadowRoot = host.attachShadow({mode: 'closed'});
const fieldset = shadowRoot.appendChild(document.createElement('fieldset'));
fieldset.setAttribute('style', 'overflow: scroll');
fieldset.innerHTML = '<slot></slot>';
</script>
<style>
*:not(fieldset, div) {
  position: sticky;
  bottom: 72pc;
}
fieldset {
  overflow: visible scroll;
}
</style>
</body>
