We attempted to disable Service Workers in Lockdown Mode in Bug 249262. However, long-term testing has shown that the Web Compatibility impact of this choice was too significant. Service Workers are foundational technology these days, and deactivating them is not viable.
This is effectively a revert of 257885@main.
<rdar://109177509>
Pull request: https://github.com/WebKit/WebKit/pull/13771
Committed 263986@main (a09166e3759c): <https://commits.webkit.org/263986@main> Reviewed commits have been landed. Closing PR #13771 and removing active labels.