Fix buffer off-by-one error.

The maximum number of Gaussian factors produces is 5.
But, 6 elements are needed to calculate those 5.

BUG=chromium:792316

Change-Id: Ief356f6c21bed7e90e33900989744c27cfe8a9a9
Reviewed-on: https://skia-review.googlesource.com/81560
Reviewed-by: Mike Klein <mtklein@chromium.org>
Commit-Queue: Herb Derby <herb@google.com>
2 files changed