When the scrolling thread latches on a node (which might be in the passive event listener region), we should also store the processing steps and used them for latched scrolls. If we don't, then we would hit-test the layers again, and potentially get a different answer (breaking the rules of latching).
Also latched scrolls need to use WheelEventProcessingSteps::MainThreadForDOMEventDispatch if in the passive region.
Created attachment 411464 [details]
Committed r268544: <https://trac.webkit.org/changeset/268544>
All reviewed patches have been landed. Closing bug and clearing flags on attachment 411464 [details].