Refactor GaussianBlur

One of the bounding boxes in this method goes haywire in DDL mode. Hopefully, this refactoring will make it easier to determine which one it is.

Note that in this CL I tried to not change the existing behavior at all.

Bug: skia:7765
Change-Id: Ie71b4c338fd7ecf4f4b8b4cb5609ef3e686eaef5
Reviewed-on: https://skia-review.googlesource.com/122956
Reviewed-by: Greg Daniel <egdaniel@google.com>
Reviewed-by: Brian Salomon <bsalomon@google.com>
Commit-Queue: Robert Phillips <robertphillips@google.com>
7 files changed