dedup tess shader flags

Change-Id: I474732cafb7d1bb8b6bdfe95fc07ecc149177ae0
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/442597
Reviewed-by: Chris Dalton <csmartdalton@google.com>
Commit-Queue: Brian Salomon <bsalomon@google.com>
1 file changed