SF: RenderEngine->drawLayers takes GraphicBuffer instead of ANativeWindow

RE interface is going to be moved to AIDL. In order to make it AIDL
compatible, drawLayer needs to take sp<GraphicBuffer> (because it's
already flattenable) instead of ANativeWindow.

Bug: 150064821
Test: atest CompositionEngineTest
Test: adb shell /data/nativetest64/.../libsurfaceflinger_unittest
Test: atest RenderEngineTest
Change-Id: Ifef487c93753d03f949f00e055a66ac6f0a98cb0