chromium/chrome/test/data/extensions/api_test/automation/sites/position.html

<!--
Copyright 2020 The Chromium Authors
Use of this source code is governed by a BSD-style license that can be
found in the LICENSE file.
-->
<html>
<head>
<title>Automation Tests - Positions</title>
</head>
<body>
<button>Tree Position</button>
<p>some text</p>
<div id='input' contenteditable><p><strong>This</strong> <b>is</b> a<em> test</em></p></div>
<script>
  const button = document.querySelector('button');
  button.addEventListener('focus', () => {
      button.remove();
  });
</script>
</body>
</html>