transform colors with steps + raster pipeline in SkColorSpaceXformer

I hate SkColorSpaceXform,
and we think this is going to be faster, especially for single colors.

Add this mode of operation to our bench from yesterday.
No surprise, it's exactly as fast as pipeA.

This may DO the TODO?

Change-Id: I1b42b42d7647d85b62cd8397bb8d6f39c4829bcf
Reviewed-on: https://skia-review.googlesource.com/145823
Reviewed-by: Brian Osman <brianosman@google.com>
Commit-Queue: Mike Klein <mtklein@google.com>
4 files changed