https://w3c.github.io/webcomponents/spec/shadow/#focus is the spec.

Gecko hasn't implemented Shadow DOM v1, and Safari hasn't caught up with it.

As discussed, sounds like the spec link in the IDL should be corrected.

Where can I check the "discussion"?

Hmm, the DOM spec needs to be updated.
https://dom.spec.whatwg.org/#dictdef-shadowrootinit

I'll handle PRs to update the spec.

Some background: the Shadow DOM spec, was originally developed as a patch
for DOM/HTML specs, but now is being upstreamed piece by piece.

kochi, there is no discussion. I think chasej meant by discussion in this thread. Thanks for updating the spec, once you've done that, please feel free to close this issue. 

Alright, thanks for the comment, lunalu@!

BTW, do you have any label for this kind of issues?

Re #8, kochi, we file everything under the umbrella bug 674593. We (predictability team) are trying to file bugs for all non-standard APIs to get them standardized or removed. 

Thanks for your help! 

This will be done in upstreaming the part of Shadow DOM spec
http://w3c.github.io/webcomponents/spec/shadow/#user-interaction
to HTML spec
https://html.spec.whatwg.org/multipage/interaction.html

Passing this to yoichio@