New window layer that voice interaction service windows
go in to. Includes a new voice-specific content rectangle
that voice activities are placed in to.
Add specific animations for this layer, sliding down from
the top (though this can be customized by the voice interaction
service).
Also add the concept of activities running for voice interaction
services for purposes of adjusting the animation used for them,
again sliding from the top, but not (yet?) customizable by the
voice interaction service.
Change-Id: Ic9e0e8c843c2e2972d6abb4087dce0019326155d
e30e02f5d9