MutationObserver shadow-dom show NotFoundError in IE11

[zhoukekestar]

Description

See the example.

Example

<script src="https://gw.alipayobjects.com/os/lib/webcomponents/webcomponentsjs/2.6.0/webcomponents-bundle.js"></script>

<div id="shadowHost"></div>
<script>
  shadowHost.attachShadow({mode:'open'}).innerHTML = '<div></div>';

  (new MutationObserver(function (mutationsList) {
    console.info('mutated');
  })).observe(shadowHost.shadowRoot, { childList: true });

  shadowHost.shadowRoot.appendChild(document.createElement('div'));

</script>

Steps to reproduce

see the example

Expected behavior

No Error

Actual behavior

NotFoundError

Version

@webcomponents/webcomponentsjs@2.6.0

Browsers affected

• [ ] Chrome
• [ ] Firefox
• [ ] Edge
• [ ] Safari
• [x] IE 11

[zhoukekestar]

[stale[bot]]

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