As per a comment by Dewei on https://bugs.webkit.org/show_bug.cgi?id=219982, we considered doing this originally, but there was not enough code to justify the change. Now there is.
<rdar://problem/72856906>
Created attachment 417099 [details] Patch
r=me
Created attachment 417218 [details] Patch for landing
Committed r271274: <https://trac.webkit.org/changeset/271274> All reviewed patches have been landed. Closing bug and clearing flags on attachment 417218 [details].
Committed r271278: <https://trac.webkit.org/changeset/271278>