vp9: Set low variance flag when partition is copied.
Also set the flag to 1 when exit early choosing 64x64 block such that skipping new mv for golden works in these scenerios. Change the size of prev_segment_id to the number of superblocks to save memory. Borg test shows quality regression of 0.012% on average PSNR and 0.035% on SSIM. Change-Id: I5014224c8617d439d35c66ece3fed9ae30b31d23
Showing with 24 additions and 5 deletions