Make sure `Clear-Site-Data: "cache"` properly clears the last back/forward cache entry.
Pull request: https://github.com/WebKit/WebKit/pull/9421
Committed 259777@main (66a67bafdb33): <https://commits.webkit.org/259777@main> Reviewed commits have been landed. Closing PR #9421 and removing active labels.
<rdar://problem/104976124>