Changed eglSwapBuffers to actually signal an error when swapBuffers
fails. This was hiding an error log at the SurfaceFlinger callsite.
When eglSwapBuffers is called after a prior error, we should not try to
enqueue a NULL buffer which was causing a segfault that takes down
SurfaceFlinger.
Bug:
33432596
Change-Id: I72f3301e0adbc4ea75266c9c1c9e01d9169036e7