Stuttery overflow scrolling in slow-scrolling regions (facebook messenger, feedly.com)
Created attachment 400091 [details] Patch
<rdar://problem/61940624>
Seems to break fast/scrolling/arrow-key-scroll-in-rtl-document.html, will investigate.
Created attachment 400104 [details] Patch
Committed r262094: <https://trac.webkit.org/changeset/262094> All reviewed patches have been landed. Closing bug and clearing flags on attachment 400104 [details].