- For all blocks with width >= 16.
- Add test_count to make the unit tests harder to pass.
- Speed testing on 1080p, 100 frames, 5 Mbps, CPU, i7-6700
  User level time reduction:
   baseline:                  3.68%
   baseline + ext-partition: 36.12%

Change-Id: I78c5d9ca216f0fd91f1a360dca2190b11fd54a08