Collapse consecutive SkTableColorFilters

BUG=skia:1366

For the added bench, the collapsing makes the bench take:
- 70% of the time for CPU rendering of 3 consecutive matrix filters
- almost no change in the GPU rendering of the matrix filters
- 50% of the time for CPU and GPU rendering of 3 consecutive table filters

Review URL: https://codereview.chromium.org/776673002
4 files changed