Jiewen pointed this out, and it's obviously true.
<rdar://problem/59053042>
Created attachment 389743 [details] Patch
unofficially r=me
rs=me
Created attachment 389805 [details] Patch for landing
Comment on attachment 389805 [details] Patch for landing Clearing flags on attachment: 389805 Committed r255813: <https://trac.webkit.org/changeset/255813>
All reviewed patches have been landed. Closing bug.