Chroma now has a list of strenghts too, with the superblock signalling
shared between luma and chroma.

low-latency, cpu=4:

   PSNR | PSNR Cb | PSNR Cr | PSNR HVS |   SSIM | MS SSIM | CIEDE 2000
-0.0114 | -1.4626 | -1.4745 |  -0.0423 | 0.0430 | -0.0001 |    -0.7416

Change-Id: I389c77f1d80020f810e45f8502c656ad9d397c8c