Set gralloc consumer usage bits in SurfaceMediaSource.

BufferQueue is no longer setting these for its endpoints; set the bits
to GRALLOC_USAGE_HW_VIDEO_ENCODER | GRALLOC_USAGE_HW_TEXTURE.  In the
longer term, the set flags should be just
GRALLOC_USAGE_HW_VIDEO_ENCODER, but that requires other changes.

Change-Id: I4170658de49bf88d829d34605a15684e72a90706