Stop using transparent region for computing visible regions (DO NOT MERGE)

The transparent region hint is computed only from view layout
locations, ignoring post-layout translation. If a SurfaceView is layed
out with no other views above it, but a view is moved above it
post-layout, that view's layout bounds would be subtracted from the
window's transparent region instead of its drawing bounds. Prior to
this change, the view would not be visible (except where its layout
bounds and drawing bounds overlap).

With this change, composition uses visible regions computed without
regard to the transparent regions. However, if all of a layer's
visible region is transparent, it will be removed from the list of
layers to composite. This doesn't fix the root problem of incorrect
transparent regions, and doesn't prevent bad composition in all cases.
But it does avoid it for some existing apps, while still allowing the
transparent region hint to save power in the important
fullscreen-video-in-a-SurfaceView case.

Change-Id: If2d929a10399b80401ef902abb232233a7f3d16d