Re: [webcomponents] [Custom Elements]: Custom elements should be display: block by default (#224)

The problem here is that it would meant that we have to do either:
 1. `display` value changes when an unresolved custom element becomes upgraded
 2. We change `display` value for all existing unknown elements with `-` in its name

I don't think we can do 2 due to backwards compatibility and 1 is very confusing for authors.  For starters, authors have to have `display: block` for `:unresolved` pseudo class or would see FOC.  If they had already specified `display: block`, then it would be mysterious that `display: block` is not needed for the actual custom elements.

---
Reply to this email directly or view it on GitHub:
https://github.com/w3c/webcomponents/issues/224#issuecomment-193491150