Add MotionEvent Matrix transformations.

Fixed issued in ViewGroup's transformation of MotionEvents to ensure
that the entire historical trace is transformed, not just the current
pointer.

Simplified the code in ViewGroup for splitting events across Views.
The new code also handles the case where some pointers are dispatched
to the ViewGroup in addition to its children whereas the previous
code would drop some pointers on the floor.

Change-Id: I56ac31903e1de8a9c376d9c935b7217b0c42d93e