add final to all the leaf SubRuns

Change-Id: I9e658accf65ce633762adef8707e9a917e535a0d
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/306058
Reviewed-by: Ben Wagner <bungeman@google.com>
Commit-Queue: Herb Derby <herb@google.com>
1 file changed