Update handling of negative std.dev for feGaussianblur/feDropShadow

Source/core/svg/SVGFEDropShadowElement.cpp

 /*
  * Copyright (C) Research In Motion Limited 2011. All rights reserved.
  *
  * This library is free software; you can redistribute it and/or
  * modify it under the terms of the GNU Library General Public
  * License as published by the Free Software Foundation; either
  * version 2 of the License, or (at your option) any later version.
  *
  * This library is distributed in the hope that it will be useful,
  * but WITHOUT ANY WARRANTY; without even the implied warranty of
@@ skipping 62 matching lines @@
 
     SVGFilterPrimitiveStandardAttributes::svgAttributeChanged(attrName);
 }
 
 PassRefPtrWillBeRawPtr<FilterEffect> SVGFEDropShadowElement::build(SVGFilterBuilder* filterBuilder, Filter* filter)
 {
     LayoutObject* layoutObject = this->layoutObject();
     if (!layoutObject)
         return nullptr;
 
-    if (stdDeviationX()->currentValue()->value() < 0 || stdDeviationY()->currentValue()->value() < 0)
-        return nullptr;
-
     ASSERT(layoutObject->style());
     const SVGComputedStyle& svgStyle = layoutObject->style()->svgStyle();
 
     Color color = svgStyle.floodColor();
     float opacity = svgStyle.floodOpacity();
 
     FilterEffect* input1 = filterBuilder->getEffectById(AtomicString(m_in1->currentValue()->value()));
     if (!input1)
         return nullptr;
 
-    RefPtrWillBeRawPtr<FilterEffect> effect = FEDropShadow::create(filter, stdDeviationX()->currentValue()->value(), stdDeviationY()->currentValue()->value(), m_dx->currentValue()->value(), m_dy->currentValue()->value(), color, opacity);
+    // Clamp std.dev. to non-negative. (See SVGFEGaussianBlurElement::build)
+    float stdDevX = std::max(0.0f, stdDeviationX()->currentValue()->value());
+    float stdDevY = std::max(0.0f, stdDeviationY()->currentValue()->value());
+    RefPtrWillBeRawPtr<FilterEffect> effect = FEDropShadow::create(filter, stdDevX, stdDevY, m_dx->currentValue()->value(), m_dy->currentValue()->value(), color, opacity);
     effect->inputEffects().append(input1);
     return effect.release();
 }
 
 } // namespace blink