See the spec bugfix at https://github.com/whatwg/streams/pull/1039 and web platform tests at https://github.com/web-platform-tests/wpt/pull/24124.
Created attachment 406078 [details] Patch
Committed r265417: <https://trac.webkit.org/changeset/265417> All reviewed patches have been landed. Closing bug and clearing flags on attachment 406078 [details].
<rdar://problem/66749555>