See issue 1030. The value of frame_parallel_decoding_mode was ignored
in vp9 if refresh_frame_context was 0, so instead make it a 3-member
enum where the dependency is obviously stated.
Change-Id: I37f0177e5759f54e2e6cc6217023d5681de92438
In vp9, [0] and [1] had identical meaning, so merge them into a
single value. Make it impossible to code RESET_FRAME_CONTEXT_NONE
for intra_only frames, since that is a non-sensical combination.
See issue 1030.
Change-Id: If450c74162d35ca63a9d279beaa53ff9cdd6612b
Define it as a function of reference frame types to provide
scalability for multiple reference frames.
Change-Id: I77b856c96916f352bc31004b9266b3f24e19bd0f
