It turns out that message order isn't defined between UI->network and UI->web->network so to ensure AddAllowedFirstPartyForCookies is processed first, use sendWithAsyncReply. Also, I'm pretty sure one of the message sending locations was redundant.
<rdar://problem/102056030>
Pull request: https://github.com/WebKit/WebKit/pull/6218
Committed 256488@main (3d4ebd0d31cd): <https://commits.webkit.org/256488@main> Reviewed commits have been landed. Closing PR #6218 and removing active labels.
*** Bug 247658 has been marked as a duplicate of this bug. ***