can not working in shadowDOM

[luichooy]

I used in shadowDOM for chrome extension to keep the markup structure, style, and behavior hidden and separate from other code on the page so that different parts do not clash, and the code can be kept nice and clean。

but now it can not working, here is a reproduction link:
https://codesandbox.io/s/angry-rhodes-9hxmg6?file=/src/index.js