Preventing parallel motion event dispatching from view system and event proxy

1) When view system is already dispatching an event, proxy-dispatch is restricted
   to gesture only and follow the gesture dispatching rule.
2) If a full-proxy-dispatch is going on, and view-dispatch comes in, view-dispatch
   takes over and proxy-dispatch is cancelled.
3) During gesture-only proxy dispatch, if view-dispatch already started a gesture,
   proxy dispatch is ignored. Otherwise view-dispatch is restricted to non-gesture
   dispatching only (and proxy-dispatch is already restricted to gesture only).

Bug: 158130948
Change-Id: Ied351663e16beda5acf49a52bdefea881c18b9cf