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>
1 file changed