Remove api call from SkGaussFilter

Simplify the SkGaussFilter API to facilitate using
ranged-for loops.

Change-Id: Id853bd6bfe342ae95b7c6248c459fbf865f75d1e
Reviewed-on: https://skia-review.googlesource.com/73262
Reviewed-by: Ben Wagner <bungeman@google.com>
Commit-Queue: Ben Wagner <bungeman@google.com>
Commit-Queue: Herb Derby <herb@google.com>
4 files changed