Update handling of negative radius for feMorphology

Update handling of negative radius for feMorphology

Spec[1] states:

 "A negative or zero value disables the effect of the given filter
  primitive (i.e., the result is the filter input image)."

So change FEMorphology to clamp radii to non-negative and stop treating
as an error in SVGFEMorphologyElement::build.

[1] https://drafts.fxtf.org/filters/#element-attrdef-femorphology-radius

BUG=533457
Committed: https://src.chromium.org/viewvc/blink?view=rev&revision=202644

[fs, 2015-09-22 19:46:43]

fs@opera.com changed reviewers:
+ fmalita@chromium.org, pdr@chromium.org, senorblanco@chromium.org

[pdr., 2015-09-22 19:53:11]

The CQ bit was checked by pdr@chromium.org

[pdr., 2015-09-22 19:53:12]

lgtm

[commit-bot: I haz the power, 2015-09-22 19:53:41]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/1344283004/1
View timeline at
 https://chromium-cq-status.appspot.com/patch-timeline/1344283004/1

[commit-bot: I haz the power, 2015-09-22 21:05:41]

Committed patchset #1 (id:1) as
https://src.chromium.org/viewvc/blink?view=rev&revision=202644

[Stephen White, 2015-09-23 13:57:29]

vacation-delayed LGTM