CSS Keywords should be lowercased during serialization: - https://www.w3.org/TR/cssom-1/#serialize-a-css-component-value
Pull request: https://github.com/WebKit/WebKit/pull/7726
Committed 258024@main (5c14835fdcfe): <https://commits.webkit.org/258024@main> Reviewed commits have been landed. Closing PR #7726 and removing active labels.
<rdar://problem/103465358>