Add threshold for partitioning blur draws

Change-Id: I67d9fd869871cdcf3c56b2b8e1048095f44c19b0
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/293337
Commit-Queue: Brian Salomon <bsalomon@google.com>
Auto-Submit: Brian Salomon <bsalomon@google.com>
Reviewed-by: Michael Ludwig <michaelludwig@google.com>
1 file changed