Optimize unread function parameter passing in SkRP.

If a function never reads from a parameter at all, we don't need
to pass it. We only need to ensure that the side effects from the
expression occur.

Change-Id: I9f0cdc11f8dcd7a0d526431fefad88efd346ece1
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/815042
Reviewed-by: Brian Osman <brianosman@google.com>
Commit-Queue: John Stiles <johnstiles@google.com>
Auto-Submit: John Stiles <johnstiles@google.com>
4 files changed