<!DOCTYPE html>
<title>Custom Elements: [HTMLConstructor] derives prototype from NewTarget</title>
<meta name="author" title="Domenic Denicola" href="mailto:d@domenic.me">
<meta name="help" content="https://html.spec.whatwg.org/multipage/dom.html#htmlconstructor">
<script src="/resources/testharness.js"></script>
<script src="/resources/testharnessreport.js"></script>
<script src="../resources/custom-elements-helpers.js"></script>
<body>
<script>
"use strict";

test_with_window(w => {
  let beforeDefinition