sksl can now fold constant vector or matrix equality expressions

Bug: skia:
Change-Id: Icaddae68e53ed3629bcdc04b5f0b541d9e4398e2
Reviewed-on: https://skia-review.googlesource.com/14260
Commit-Queue: Ethan Nicholas <ethannicholas@google.com>
Reviewed-by: Ben Wagner <benjaminwagner@google.com>
8 files changed