The parallel_deblocking experiment is proposed jointly by Intel
and Microsoft. The following changes are implemented in this
experiment:

- deblocking filter order is changed to filter all vertical edges
  of the whole frame followed by filtering all horizontal edges
  of the whole frame

- filter length decision is made based on the transform block size
  on both sides of the edge. block with smaller transform size
  determines the final filter length.

- transform blocks on both sides of the edge are checked, only when
  both blocks are skipped and they belong to the same prediction
  block, filtering of that edge can be skipped.

- 15-tap filter and extended flat area detection are removed.

- special rule for handling 4x4 transform block on the super block
  boundary in VP9 is removed.

Change-Id: I1aa82c6b5335d47c2f73eec8fc8bee2c08a1cf74