SurfaceFlinger: Add support for virtual display

- Creates a rendering surface when invoked via hybrid path
- Makes changes in HWC wrapper to handle virtual display via HWC

Change-Id: I86560b5009949b75c267249799a446b8279eff32
Conflicts:
services/surfaceflinger/SurfaceFlinger.h
services/surfaceflinger/SurfaceFlinger.cpp
2 files changed