Move the initial GrProgramDesc keyLength into the header

This sets up for moving GrProgramDesc creation to GrCaps. I.e., we will have a virtual "GrProgramDesc GrCaps::makeDesc(const GrRenderTarget*, const GrProgramInfo&)" call.

Bug: skia:9455
Change-Id: I82053297383af9d405e6b485bf8287f10fa15967
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/256696
Reviewed-by: Greg Daniel <egdaniel@google.com>
Commit-Queue: Robert Phillips <robertphillips@google.com>
4 files changed