'all' and the system focus outline

The 'all' property, when you "all: initial" or "all: unset", also
resets the 'outline' property.  This is troublesome, because, for a11y
reasons, you don't want to kill the outline of an element by accident.
You can restore it manually, but that's not something that most people
will do, because it's not obvious that you have to do it.

This is likely not *directly* overriding the outline styles, as
they're on button:focus or whatever. But if your selector has at least
one element and one class worth of specificity, it'll win in the
cascade even when the element is focused.

I don't know how to fix this. :/  We probably dont' want to exclude
'outline' from being reset by 'all'; unlike 'direction' and
'unicode-bidi', it's a valid property, and wanting to reset it when
you're using it for something *other than* focus outlines is valid.

~TJ