Fix constant output for Clamp FP when child processor is present.

Change-Id: I0ff358665c77b9826ee76befc4490b2204f2fa4a
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/294698
Reviewed-by: Brian Osman <brianosman@google.com>
Commit-Queue: John Stiles <johnstiles@google.com>
2 files changed