Resync web-platform-tests/background-fetch from upstream.
Created attachment 404588 [details] Patch
Comment on attachment 404588 [details] Patch r=me
Committed r264542: <https://trac.webkit.org/changeset/264542> All reviewed patches have been landed. Closing bug and clearing flags on attachment 404588 [details].
<rdar://problem/65748448>