Add "meshCount" to GrProgramInfo This improves the encapsulation of the GrProgramInfo class. Bug: skia:9455 Change-Id: Ic241ba4a2c2edea3e774522065371e5ed8cc2da3 Reviewed-on: https://skia-review.googlesource.com/c/skia/+/247438 Commit-Queue: Robert Phillips <robertphillips@google.com> Reviewed-by: Greg Daniel <egdaniel@google.com>