Without turning it on yet, of course.
The reason why I didn't use the general PseudoElement mechanism is because this
pseudo is a bit of its own thing, and I found easier to make ::selectors know
about it (because you need to jump to the assigned slot) than the other way
around.
Also, we need to support ::slotted(..)::before and such, and supporting multiple
pseudo-elements like that breaks some other invariants around the SelectorMap,
and fixing those would require special-casing slotted a lot more in other parts
of the code.
Let me know if you think otherwise.
I also don't like much the boolean tuple return value, but I plan to do some
cleanup in the area in a bit, so it should go away soon, I'd hope.
Right now we go through a lot of hoops to see if we ever see a relevant link.
However, that information is not needed: if the element is a link, we'll always
need to compute its visited style because its its own relevant link.
If the element inherits from a link, we need to also compute the visited style
anyway.
So the "has a relevant link been found" is pretty useless when we know what are
we inheriting from.
The branches at the beginning of matches_complex_selector_internal were
affecting performance, and there are no good reasons to keep them.
I've verified that this passes all the visited tests in mozilla central, and
that the test-cases too-flaky to be landed still pass.
This type is a lot of complexity related to a very specific thing such as the
hover and active quirk.
Instead of that, move `nesting_level` to `MatchingContext`, and simplify all
this computing whether the quirk applies upfront, for each complex selector we
test.
This is less error-prone, and also allows simplifying more stuff in a bit.
Adjust the matching process to look for a "relevant link" while matching. A
"relevant link" is the element being matched if it is a link or the nearest
ancestor link.
Matching for links now depends on the `VisitedHandlingMode`, which determines
whether all links match as if they are unvisited (the default) or if the
relevant link matches as visited (and all others remain unvisited).
If a relevant link is ever found for any selector, track this as part of the
`MatchingContext` object. This is used in the next patch to determine if an
additional match and cascade should be performed to compute the styles when
visited.
MozReview-Commit-ID: 3xUbRo7vpuD
