Revert "replace SkColorSpaceXformSteps::Required()"

This reverts commit 122eda78775301bb28f467d30ad5edb95dad8df2.

Reason for revert: breaking up into parts to help diagnose a possible performance regression.

Original change's description:
> replace SkColorSpaceXformSteps::Required()
> 
> It's error-prone to ask if a color space transform is required without
> explicitly mentioning alpha types.  I think the whole method can be
> replaced by a friendlier constructor and direct use of flags/mask:
> 
>     SkColorSpaceXformSteps::Required(src.colorSpace(), dst.colorSpace())
> 
>         ~~~>
> 
>     0 != SkColorSpaceXformSteps(src, dst).flags.mask()
> 
> This removes the unexpected gray square from the fiddle in skia:9662.
> 
> Bug: skia:9662
> Change-Id: Id54cae534023ab29c94dcc149e6b67fc9c166665
> Reviewed-on: https://skia-review.googlesource.com/c/skia/+/257399
> Reviewed-by: Brian Osman <brianosman@google.com>
> Commit-Queue: Mike Klein <mtklein@google.com>

TBR=mtklein@google.com,brianosman@google.com

Change-Id: I4073f45c52e77f02fe3ecb75c20fc29873080c20
No-Presubmit: true
No-Tree-Checks: true
No-Try: true
Bug: skia:9662
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/257652
Reviewed-by: Mike Klein <mtklein@google.com>
Commit-Queue: Mike Klein <mtklein@google.com>
5 files changed