Code review comment for lp:~kdub/mir/overlay-gl-program

I think I'm convinced that it should be a separate program.

However it should be a very simple fallback - that is no resize support and no handling of screen rotation; I believe what is proposed here satisfies that.

If those features are needed, then it should fallback to the path we currently have (with GLRenderer).

So: hwc->prepare(..)
If all layers accepted - great - nothing else to do.
If some layers got rejected and need screen rotation/resizing - fallback to GLRenderer path - composite all layers with GLRenderer - essentially the path we use currently.
Otherwise fallback so simple hwc fallback GL compositor.

Needs fixing:
OverlayGLProgram - my suggestion is HWCFallbackGLRenderer to make it real clear what is responsiblity is.
OverlayCompositor - like Cemil says once rejected they are not "overlays" per se. So my suggestions is HWCFallbackCompositor