Revert "Revert "Make SkASSERT not break build in constexpr GrSwizzle method on GCC""

This reverts commit 27239e456abd1bf3664470b90563343db6191b1f.

Revert "Revert "Add function to GrDataUtils to handle color conversions.""

This reverts commit c34d993b62a570181506dd54cd4a8e02b9c38315.

Change-Id: Iac1bdaa6f8380e63bbb87394e7fca96808572131
Bug: skia:8962
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/222039
Reviewed-by: Brian Salomon <bsalomon@google.com>
Commit-Queue: Brian Salomon <bsalomon@google.com>
15 files changed