Re: [webcomponents] Disallow attachShadow(...) for some elements. (#110)

I'd like to move this issue forward.

As the first step, can we agree on having a white list?
The initial white list might be:

- Any custom elements
- `div`
- `span`

We can expand this white list anytime if we can agree on adding an element to this list. If we can feel that having a white list is hard to maintain, we can switch to having a blacklist.

---
Reply to this email directly or view it on GitHub:
https://github.com/w3c/webcomponents/issues/110#issuecomment-177821510