Add comment for RD_STATS
Add comment for RD_STATS

Change-Id: I30a6de3f7eb0c5ef3285ae62c39b3d14a94bd649

GrokImageCompression/aom,GrokImageCompression/aom,GrokImageCompression/aom,GrokImageCompression/aom,GrokImageCompression/aom,GrokImageCompression/aom