pull out calculation of SDF ops parameters

Change-Id: Ifc3909a93ae036fc8f851cf0a8ea9cc65b688b34
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/375064
Commit-Queue: Herb Derby <herb@google.com>
Reviewed-by: Robert Phillips <robertphillips@google.com>
1 file changed