[Async overflow scrolling] Slow-repaint overflow scroll have force their enclosing scrollers to be slow too
Created attachment 396619 [details] Patch
Created attachment 396624 [details] Patch
Committed r260190: <https://trac.webkit.org/changeset/260190> All reviewed patches have been landed. Closing bug and clearing flags on attachment 396624 [details].
<rdar://problem/61888269>