Up motion event not injected by the touch explorer at the end of a drag.

1. The up event was not injected when the last pointer went up, i.e.
   at the end of the drag. This patch sends an up event if the dragging
   pointer goes up for both cases, when the dragging pointer goes up
   first and when it goes up second.

bug:7272830

Change-Id: I708a2b93ee2d0a4c46dbeea002841666e919602d