skslc comma operator and optimizer fixes

Bug: skia:
Change-Id: I732d4fba843c06af570d4a56cadfaa1cc565808c
Reviewed-on: https://skia-review.googlesource.com/17125
Commit-Queue: Ethan Nicholas <ethannicholas@google.com>
Reviewed-by: Ben Wagner <benjaminwagner@google.com>
9 files changed