Re: [css-selector] :focus and shadow host

Thanks Tab, for all the comments.

IIUC the 'tab group' thing is a recurring discussion and it may be high
time for
considering seriously.

I must admit that the interaction of tabindex and tabstop is very confusing,
even for me, and already found some defects that it cannot explain
an <a> behavior (with custom elements + shadow dom) completely,
so I would like to explore fleshing out 'tab group' and 'isTabGroup' idea.

At the same time, I've almost finished the experimental tabstop
implementation
for Blink (behind experimental web platforms flag).
https://codereview.chromium.org/1046853002/
is the last patch (under review) for attribute <-> property reflection.

The basic rule is, unless HTML "tabstop" attribute is there (if tabStop
property
is set via script, it is reflected in HTML attribute, so there is), tabStop
reflects what tabindex for the element means.

I'll see how this can or cannot fit for e.g. creating a custom <input-date>
etc.