Make frame-wide filter-type decision fully RD-based.

Overall, on all test sets, this gains about +0.2% on all metrics.
City is a clip where this really hurts (-1.0% on all metrics), I'm
not quite sure why yet. Maybe interesting to look into in the future.

Change-Id: I6f0eecb20e72f0194633270d30bf00d76d9eae78