Web Locks API does get enabled in Service Workers when running layout tests.
Created attachment 444551 [details] Patch
Comment on attachment 444551 [details] Patch r=me
Committed r285954 (244355@main): <https://commits.webkit.org/244355@main> All reviewed patches have been landed. Closing bug and clearing flags on attachment 444551 [details].
<rdar://problem/85521215>