Revert "Add an average mode for sigma < 2"

This reverts commit ba8275148ab8b10393b053e2586b852796c4afc2.

Reason for revert: layout tests, Google3 equivalent failing.

Original change's description:
> Add an average mode for sigma < 2
> 
> The original code had an optimization when sigma < 2 that averaged
> pixels instead of Gaussian bluring them. This CL adds that
> behavior back to the new implementat.
> 
> BUG=chromium:745290
> Change-Id: I35b7de2138a859d546439cc2053b4b599a94ebe1
> Reviewed-on: https://skia-review.googlesource.com/34180
> Commit-Queue: Herb Derby <herb@google.com>
> Reviewed-by: Mike Klein <mtklein@chromium.org>

TBR=mtklein@chromium.org,mtklein@google.com,herb@google.com

Change-Id: Ie8f38b042acec42260913cb7bed5538a2c957e9b
No-Presubmit: true
No-Tree-Checks: true
No-Try: true
Bug: chromium:745290
Reviewed-on: https://skia-review.googlesource.com/34640
Reviewed-by: Mike Klein <mtklein@google.com>
Commit-Queue: Mike Klein <mtklein@google.com>
2 files changed