Converted OPERATOR_RIGHT macro into a function

No functional changes; just a code cleanup now that this is possible.

Change-Id: I2d153e22058c2b9be8e1dc4f2ad9ccc186bff120
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/527657
Reviewed-by: John Stiles <johnstiles@google.com>
Commit-Queue: Ethan Nicholas <ethannicholas@google.com>