Reduce wasted buffer allocations

Bug: 20170924

Don't pre-allocate buffers if there is a SurfaceView or other
View that has requested transparent regions. This doesn't fully
address the problem of allocating buffers when there's a full
screen SurfaceView but it at least gets back to KitKat levels
of only having 1 wasted buffer instead of 3 (the 1 being
a result of the fact that it will still draw one frame of emptiness
forcing a buffer dequeue).

Change-Id: Ied9553186bc7b111d180b63f87b92bd317cb4b97