Created attachment 396698 [details]
Start a slow swipe over an overflow:scroll, and we'll always latch on the main frame by mistake.
The first event we get has zero deltas, so ScrollingTreeScrollingNode::canScrollWithWheelEvent() returns false for non-root nodes, and true for root nodes. Then we latch on the root node for the rest of the gesture.
Created attachment 396703 [details]
Committed r260224: <https://trac.webkit.org/changeset/260224>
All reviewed patches have been landed. Closing bug and clearing flags on attachment 396703 [details].