Touch explorer and magnifier do not work well together.

1. If tocuh exploration and screen magnification are enabled and the screen
   is currently magnified, gesture detection does not work well. The reason
   is because we are transforming the events if the screen is magnified before
   passing them to the touch explorer to compensate for the magnification so
   the user can poke what he thinks he pokes. However, when doing gesture
   detection/velocity computing this compensating shrinks the gestured shape/
   decreases velocity leading to poor gesture reco/incorrect velocity.

   This change adds a onRawMotionEvent method in the event transformation chain
   which will process the raw touch events. In this method of the touch explorer
   we are passing events to the gesture recognized and the velocity tracker.

2. Velocity tracker was not cleared on transitions out of touch exploring state
   which is the only one that uses velocity.

bug:7266617

Change-Id: I7887fe5f3c3bb6cfa203b7866a145c7341098a02