Shadow host with its .tabindex property -1 would be skipped for focus navigation

[TakayoshiKochi]

Context:
#554 (comment)

In the Shadow DOM spec 6.3
http://w3c.github.io/webcomponents/spec/shadow/#sequential-focus-navigation
specifically in Step 3.1.3, all elements with negative tabindex value will be skipped in the focus navigation, but shadow hosts with delegatesFocus=faluse should be excluded otherwise all focusable elements in its shadow root will never visited.

[rniwa]

@rakina : This issue seems still relevant.

[rakina]

Yes, the whole flat tree will be skipped when the host has negative tabindex value, as currently specced. Is there any interest in changing that?

[rniwa]

@rakina : I guess the users of a component decided to set tabIndex to be -1 then it's probably sensible to treat it such.

I was thinking about focusing via mouse click and such but those aren't affected by this because we've isolated that to use the first focusable element in the flat tree order.

[rniwa]

@smaug---- @annevk : I think we can close this issue now. WDYT?

[smaug----]

Yes, if one uses -1 on the host, the shadow DOM shouldn't get focused. Fine to close