TIF: implement gatherTransparentRegion() and dispatchDraw() in TvView.

Background: because the hole-punching code lives only in SurfaceView,
the overlay view can be covered by the application if the TV input
changes the position of SurfaceView via Session.layoutSurface().
This change punches a hole as large as TvView so that the underlying
overlayview can be shown properly.

Bug: 18420642
Change-Id: If9a829367083ce2002a4c4a4e4a4bbb623f7ad96