Add proper support for StylePropertyMap: - https://drafts.css-houdini.org/css-typed-om/#stylepropertymap
Pull request: https://github.com/WebKit/WebKit/pull/5632
Committed 255964@main (dcf5f3833e1e): <https://commits.webkit.org/255964@main> Reviewed commits have been landed. Closing PR #5632 and removing active labels.
<rdar://problem/101547554>