...and replace it with AngleOrCalculated.
This has the nice bonus effect of actually handling `calc()` for angles
in a transform function. :^) (Previously we just would have asserted.)
This is intended as a replacement for Length and friends each holding a
`RefPtr<CalculatedStyleValue>`. Instead, let's make the types explicit
about whether they are calculated or not. This then means a Length is
always a Length, and won't require including `StyleValue.h`.
As noted, it's probably nicer for LengthOrCalculated to live in
`Length.h`, but we can't do that until Length stops including
`StyleValue.h`.
Due to CSSImportRule::has_import_result() being backwards, we never
actually entered imported style sheets when traversing style rules or
media queries.
With this fixed, we no longer need the "collect style sheets" step in
StyleComputer, as normal for_each_effective_style_rule() will now
actually find all the rules. :^)
This was causing a huge slowdown when loading some pages with weirdly
huge number of style sheets. For example, amazon.com has over 200 style
elements, which meant we had to resort the StyleSheetList 200 times.
(And sorting itself was slow because it has to compare DOM positions.)
Instead of sorting, we now look for the correct insertion point when
adding new style sheets, and we start the search from the end, which is
where style sheets are typically added in the vast majority of cases.
This removes a 600ms time sink when loading Amazon on my machine! :^)
Previously we used a parsing context with no access to the document, so
any URLs in url() functions would become invalid.
Fixes the images on Steam's store carousel, which sets
Element.style.backgroundImage to url() functions.
Some versions of clang, such as Apple clang-1400.0.29.202 error out on
the previous out of line operators. Explicitly defaulting comparison
operators out of line is allowed per P2085R0, but was checked in clang
before version 15 in C++20 mode.
