The main objective is to reduce computational complexity.
The domain transform filter has an effect of edge preserving smoothing
at a lower computational cost than the bilateral filter, and can be
readily paralelized.

A little drop in coding efficiency about 0.06% for lowres, 0.16% for
midres.

Change-Id: Id949406b7e5afe9b64588d130065c63a76e4f3f9