This reverts 0e3487b9ab.
Back when I made that change, I thought we could make our StyleValue
classes match the typed-om definitions directly. However, they have
different requirements. Typed-om types need to be mutable and GCed,
whereas StyleValues are immutable and ideally wouldn't require a JS VM.
While I was already making such a cataclysmic change, I've moved it into
the StyleValues directory, because it *not* being there has bothered me
for a long time. 😅
To support this, how we declare logical property aliases has changed.
Instead of `logical-alias-for` being a list of properties, it's now an
object with a `group` and `mapping`. The group is the name of a logical
property group in LogicalPropertyGroups.json. The mapping is which
side/dimension/corner this property is. Hopefully it's self-explanatory
enough.
The generated code is very much a copy of what was previously in
`StyleComputer::map_logical_alias_to_physical_property_id()`, so there
should be no behaviour change.
CSSStyleDeclaration is a base class that's used by various collections
of style properties or descriptors. This commit moves all
style-property-related code into CSSStyleProperties, where it belongs.
As noted in the previous commit, we also apply the CSSStyleProperties
prototype now.
We previously had PropertyOwningCSSStyleDeclaration and
ResolvedCSSStyleDeclaration, representing the current style properties
and resolved style respectively. Both of these were the
CSSStyleDeclaration type in the CSSOM. (We also had
ElementInlineCSSStyleDeclaration but I removed that in a previous
commit.)
In the meantime, the spec has changed so that these should now be a new
CSSStyleProperties type in the CSSOM. Also, we need to subclass
CSSStyleDeclaration for things like CSSFontFaceRule's list of
descriptors, which means it wouldn't hold style properties.
So, this commit does the fairly messy work of combining these two types
into a new CSSStyleProperties class. A lot of what previously was done
as separate methods in the two classes, now follows the spec steps of
"if the readonly flag is set, do X" instead, which is hopefully easier
to follow too.
There is still some functionality in CSSStyleDeclaration that belongs in
CSSStyleProperties, but I'll do that next. To avoid a huge diff for
"CSSStyleDeclaration-all-supported-properties-and-default-values.txt"
both here and in the following commit, we don't apply the (currently
empty) CSSStyleProperties prototype yet.
