While analyzing the difference between overflow node and subframes, I noticed that frame views don't do anything special for FrameView::didStartScroll, FrameView::didEndScroll and FrameView::didUpdateScroll, contrary to overflow layers. I am not sure whether it is actually needed for subframes? Moreoever for overflow node, it seems that it is only used when ENABLE_TOUCH_EVENTS is enabled which I can not try without the private iOS SDK (bug 179167).
Created attachment 325715 [details]
Patch (not tested)