<!DOCTYPE html>
<meta charset="utf-8">
<title>Adoptedstylesheets.concat should work when starting empty</title>
<link rel="author" href="mailto:masonf@chromium.org">
<link rel="help" href="https://drafts.csswg.org/cssom/#extensions-to-the-document-or-shadow-root-interface">
<link rel="match" href="CSSStyleSheet-constructable-concat-ref.html">
<script src="/resources/testharness.js"></script>
<script src="/resources/testharnessreport.js"></script>

<span>This should be green</span>
<div id=host></div>

<scri