Revert of second try at landing improved blur rect (https://codereview.chromium.org/325703002/)

Reason for revert:
broke some fast/canvas layout tests

Original issue's description:
> second try at landing improved blur rect
>
> BUG=skia:2095
> TBR=bsalomon
>
> Committed: https://skia.googlesource.com/skia/+/e9ea0d6b7d59ac3b7e257281e545b24bcc0d2a76

R=bsalomon@google.com, reed@chromium.org, humper@google.com
TBR=bsalomon@google.com, humper@google.com, reed@chromium.org
NOTREECHECKS=true
NOTRY=true
BUG=skia:2095

Author: reed@google.com

Review URL: https://codereview.chromium.org/322423002
4 files changed