Update web-platform-tests/interfaces from upstream.
Created attachment 400524 [details] WIP Patch
Created attachment 400526 [details] Patch
Created attachment 400539 [details] Patch
Committed r262277: <https://trac.webkit.org/changeset/262277> All reviewed patches have been landed. Closing bug and clearing flags on attachment 400539 [details].
<rdar://problem/63743498>
Reopening to attach new patch.
Created attachment 400583 [details] Patch
Already landed.