SF: black out layers that doesn't have gpu accessible buffer

If a layer provided a non gpu readable buffer, and that layer needs
to be composited using the gpu, backout the layer instead of asserting
in RenderEngine.

Fixes: 183950013
Test: launch the apk attached to the bug and force client composition
Change-Id: I068d72acf58866150284b3770b7c33da5a3bd3ac
1 file changed