Add a bench for various single color xforms

PipeA is where we want to be, and probably by filling in something
like the TODO I left in SkColorSpaceXformSteps.h?

    curr/maxrss	loops	min	median	mean	max	stddev	samples   	config	bench
      13/13  MB	49	82.8ns	83.2ns	83.2ns	84.1ns	0%	█▂▅▄▂▁▃▄▃▃	nonrendering	ColorSpaceXformBench_pipeB
      13/13  MB	1259	29.6ns	29.7ns	30.4ns	37.2ns	8%	▁▁▁▁▁▁▁▁▁█	nonrendering	ColorSpaceXformBench_pipeA
      13/13  MB	661	110ns	119ns	119ns	128ns	4%	▅▅▅▅▅▅▅▅█▁	nonrendering	ColorSpaceXformBench_steps
      13/13  MB	26	239ns	247ns	283ns	609ns	40%	▁▁█▁▁▁▁▁▁▁	nonrendering	ColorSpaceXformBench_xform

Change-Id: I98af634ab0a7a1522a5bcfde9ce3fc934d82ecf8
Reviewed-on: https://skia-review.googlesource.com/145643
Commit-Queue: Mike Klein <mtklein@google.com>
Auto-Submit: Mike Klein <mtklein@google.com>
Reviewed-by: Brian Osman <brianosman@google.com>
3 files changed