Reland "Workaround constexpr bug in MSVC 2015 in GrTextureOp"

This is a reland of 9eff78e2623d600282ca63c2e9988e0ffbba2949

Original change's description:
> Workaround constexpr bug in MSVC 2015 in GrTextureOp
> 
> Change-Id: I441858aab5fcd63e5467625a23681c5bcd35f25b
> Reviewed-on: https://skia-review.googlesource.com/130122
> Reviewed-by: Brian Osman <brianosman@google.com>
> Commit-Queue: Brian Salomon <bsalomon@google.com>

Change-Id: I90e5d807f658baadfab80333d84872d8105bf02b
Reviewed-on: https://skia-review.googlesource.com/130306
Reviewed-by: Stephen White <senorblanco@chromium.org>
1 file changed