Expose bounds for maskfilters

Bug: skia:12094
Change-Id: Ia0dfa15fef2cd2f5fe7e024e085e56880c12224b
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/419098
Reviewed-by: Brian Osman <brianosman@google.com>
Commit-Queue: Mike Reed <reed@google.com>
4 files changed