Add unit test demonstrating output from Gaussian blur.

Change-Id: I1be21b428939d17bbf3a9347a64db56c7cd69eb4
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/337638
Commit-Queue: John Stiles <johnstiles@google.com>
Commit-Queue: Brian Osman <brianosman@google.com>
Auto-Submit: John Stiles <johnstiles@google.com>
Reviewed-by: Brian Osman <brianosman@google.com>
5 files changed