Implement constant folding for vector*scalar ops.

Change-Id: I96b547de4fe4b73096fb26d0ef21a4e7555ca06a
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/352238
Commit-Queue: John Stiles <johnstiles@google.com>
Auto-Submit: John Stiles <johnstiles@google.com>
Reviewed-by: Brian Osman <brianosman@google.com>
2 files changed