CSSSelectorList is an optimized data structure which takes some time to construct. We should doing it too early or when it's unnecessary.
<rdar://problem/118931010>
Pull request: https://github.com/WebKit/WebKit/pull/21052
Committed 271290@main (3ff376ea3d2a): <https://commits.webkit.org/271290@main> Reviewed commits have been landed. Closing PR #21052 and removing active labels.