'my-input'>
<script>
test(t => {
  const input = document.getElementById('customized-input');
  assert_true(input instanceof MyInput);
  assert_true(input instanceof HTMLInputElement);
}, 'Make sure customized <input> element doesnt crash');
</script>


<script>
class MyInputAttrs extends HTMLInputElement {
  constructor() {
    super();
    this.setAttribute('foo', 'bar');
  }
}
customElements.define('my-input-attr', MyInputAttrs, { extends: 'input' });
</script>
<input id=customized-input-attr is='my-inpu