Resync web-platform-tests/xhr from upstream.
Created attachment 451390 [details] Patch
Created attachment 451421 [details] Patch
Created attachment 451470 [details] Patch
Committed r289540 (247071@main): <https://commits.webkit.org/247071@main> All reviewed patches have been landed. Closing bug and clearing flags on attachment 451470 [details].
<rdar://problem/88758236>