Move InterpretSampling to its one caller

No functional change, but this "helper" is now only called in one place.

Just part of my cleaning house around filtering logic. Happy to leave
things as they were if that is preferred.

Change-Id: I9131354240295af2d2041f759c24fc1d4805502e
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/387437
Commit-Queue: Mike Reed <reed@google.com>
Reviewed-by: Michael Ludwig <michaelludwig@google.com>
Reviewed-by: Brian Salomon <bsalomon@google.com>
3 files changed