GesturePinch* event sequence received at TouchActionFilter seems broken.

The pinch gesture sequence:
- a pinch zoom-out (with fingers getting closer) then
- a pinch zoom-in (with fingers getting farther)
dispatches the following sequence of events to TouchActionFilter

  GestureTapDown
  GestureTapCancel
  GestureScrollBegin
  GestureScrollUpdate+
  GesturePinchBegin
  (GestureScrollUpdate & GesturePinchUpdate)+
  GestureScrollUpdate
  GesturePinchEnd
  GestureScrollUpdate+
  GesturePinchBegin
  (GestureScrollUpdate & GesturePinchUpdate)+
  GesturePinchEnd
  GestureScrollEnd

The pinch event sequence seems to end & restart prematurely somewhere in the second step, producing two GesturePinchBegin/End pairs.

Expected: GestureScrollBegin/End should bracket a single GesturePinchBegin/End pair.

Related notes:
- Switching the two steps (zoom-in then zoom-out) doesn't seem to show the problem.
- I suspect repeated zoom-out-and-in continuously would produce repeated premature breaks.