Avoid code duplication between ComputedStylePropertyMapReadOnly and MainThreadStylePropertyMapReadOnly by having ComputedStylePropertyMapReadOnly subclass MainThreadStylePropertyMapReadOnly instead of the more generic StylePropertyMapReadOnly.
Pull request: https://github.com/WebKit/WebKit/pull/7006
Committed 257284@main (95de65d62997): <https://commits.webkit.org/257284@main> Reviewed commits have been landed. Closing PR #7006 and removing active labels.
<rdar://problem/102905789>