Simplify usage of GrGLSLColorSpaceXformHelper

It was already safe to call setData without (redundantly) checking
isValid, so remove those. Made the emitCode helpers safe, too, so that
we only need to check for isValid in one spot. Then, because it made
more sense, invert the logic and rename it to isNoop().

Pulled out of https://skia-review.googlesource.com/c/skia/+/132090

Bug: skia:
Change-Id: I147fa2e0a06c04024c6aa98725fa73501044e4cd
Reviewed-on: https://skia-review.googlesource.com/134948
Commit-Queue: Mike Klein <mtklein@google.com>
Auto-Submit: Brian Osman <brianosman@google.com>
Reviewed-by: Mike Klein <mtklein@google.com>
6 files changed