Move PropertyNameAndID, custom property data, registered custom
properties, and Typed OM associated property names to Utf16FlyString.
This removes the FlyString storage boundary from CSS property-name
handling and lets CSSStyleProperties keep the name it receives from
CSSOM instead of converting it back to UTF-8.
After `Native.css` was removed in the last commit only
`libweb-buttonfacedisabled` and `libweb-buttonfacehover` remain in use,
so the rest can be removed.
Resolving these colors was also the only use of `document` in
`ColorResolutionContex` so we can remove that too.
Previously we overrode the resolved values of the `activetext`,
`linktext`, and `visitedtext` system colors based on the values of the
body's `alink`, `link`, and `vlink` attributes respectively.
This was incorrect and the spec instead expects us to apply these to the
relevant link elements as presentational hints while leaving those
colors untouched for other users.
While the spec says that `accentcolor` and `accentcolortext` resolve
relative to the `accent-color` property this isn't implemented by any
other browsers.
This effectively reverts d04b745 but doesn't change behavior since that
was already done in 92897a1.
These get computed to an equivalent RGBColorStyleValue.
To support this, we now store the computed color-scheme on the
ComputationContext when computing properties that might contain a color.
This has a nice bonus of correcting the css-accent-color test's result.
Previously, some StyleValues created a large number of intermediate
strings during serialization. Passing a StringBUilder into the
serialization function allows us to avoid a large number of these
unnecessary allocations.
For us, that's KeywordStyleValue and CustomIdentStyleValue.
CustomIdentStyleValue now has a .cpp file to reduce the number of
includes in its header file.
