 document.body.appendChild(container);
  // inneHTML upgrades my-control at its CEReacions timing.
  container.innerHTML = '<my-control disabled>';
  assert_array_equals(container.firstChild.disabledHistory(), [true]);

  container.innerHTML = '<fieldset disabled><my-control>';
  assert_array_equals(container.querySelector('my-control').disabledHistory(), [true]);
}, 'Upgrading an element with disabled content attribute');

test(() => {
  const container = document.createElement('div');
  document.body.appe