Programmatic scroll of overflow:scroll does the wrong thing (it clobbers the UIScrollView contentOffset with 0,0).
Marked compositing/ios/overflow-scroll-update-overlap.html as failing for now in https://trac.webkit.org/changeset/242758/webkit
We need the same logic we have for "requestedScrollPositionUpdate" for overflow that we have for Frames.
Created attachment 364342 [details]
Work in progress
Need to do some cleanup work before this to move isHandlingProgrammaticScroll from ScrollingTree to the scrolling node, and make frames/overflow more similar for programmatic scroll.