Merge changes I90625ae0,I96aaa686,I0f6584e1,I75219370,I68ed3bee

* changes:
  Modifies the PipMotionHelper to use PhysicsAnimator for PIP motion.
  Fix issue with left-flings when distanceToDestination = 0.
  Add FloatProperties, which contains helpful properties for animating Rects.
  Filter end actions for null, and allow Runnables from Java
  Cancel flings before restarting them.