Added missing validation

Added missing validation

BUG=433359
Committed: https://skia.googlesource.com/skia/+/1379b87ae463246e586b869f7457ce5befc4472c

[sugoi1, 2014-11-14 18:32:21]

sugoi@chromium.org changed reviewers:
+ reed@google.com

[sugoi1, 2014-11-14 18:32:46]

sugoi@chromium.org changed reviewers:
+ bsalomon@google.com

[reed1, 2014-11-14 18:55:18]

I don't know how kernelOffset is used.

[sugoi1, 2014-11-14 19:02:41]

On 2014/11/14 18:55:18, reed1 wrote:
> I don't know how kernelOffset is used.

It's used in SkMatrixConvolutionImageFilter::filterPixels to move/slide the
kernel around the central point being filtered, I think.

[bsalomon, 2014-11-14 19:34:07]

bsalomon@google.com changed reviewers:
+ senorblanco@chromium.org

[bsalomon, 2014-11-14 19:34:08]

I think Stephen would be the right person to review this.

[Stephen White, 2014-11-14 21:27:04]

LGTM

[sugoi1, 2014-11-17 13:37:04]

The CQ bit was checked by sugoi@chromium.org

[commit-bot: I haz the power, 2014-11-17 13:37:41]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/729583002/1

[commit-bot: I haz the power, 2014-11-17 13:45:59]

Committed patchset #1 (id:1) as
https://skia.googlesource.com/skia/+/1379b87ae463246e586b869f7457ce5befc4472c