<!DOCTYPE html>
<style>
div { color: green; }
</style>
<p>Test passes if you see a single 100px by 100px green box below.</p>
<iframe></iframe>
<script>
const frameDocument = document.querySelector('iframe').contentDocument;
frameDocument.body.innerHTML = `<div></div>`;
const host = frameDocument.querySelector('div');
host.attachShadow({mode:'closed'}).innerHTML = `
    <style>
    :host {
        color: red;
        background: green;
        width: 100px;
        height: 100px;
    }
    </style>
    <span>Test moving a host to a different document.</span>
`;
host.offsetWidth;
document.adoptNode(host);
document.body.appendChild(host);
document.body.removeChild(document.querySelector('iframe'));
if (window.GCController)
    GCController.collect();
</script>