Clamp negative sigma to 0 in SkDropShadowImageFilter.

Clamp negative sigma to 0 in SkDropShadowImageFilter.

This can occur when the matrix includes a perspective transform.

BUG=skia:2094
R=bsalomon@google.com

Committed: https://code.google.com/p/skia/source/detail?r=13220

[Stephen White, 2014-01-28 17:49:26]

PTAL. Thanks!

[bsalomon, 2014-01-28 17:51:05]

On 2014/01/28 17:49:26, Stephen White wrote:
> PTAL. Thanks!

lgtm, but style nit

if (sigma.fX < 0) {
  sigma.fX = 0;
}

-or-

sigma.fX = SkTMax(0, sigma.fX);

[Stephen White, 2014-01-28 17:54:47]

On 2014/01/28 17:51:05, bsalomon wrote:
> On 2014/01/28 17:49:26, Stephen White wrote:
> > PTAL. Thanks!
> 
> lgtm, but style nit
> 
> if (sigma.fX < 0) {
>   sigma.fX = 0;
> }
> 
> -or-
> 
> sigma.fX = SkTMax(0, sigma.fX);

Fixed (using SkScalarMax for clarity)

[bsalomon, 2014-01-28 17:57:17]

lgtm

[Stephen White, 2014-01-28 17:57:29]

Committed patchset #2 manually as r13220 (presubmit successful).