Update handling of negative std.dev for feGaussianblur/feDropShadow

Source/core/svg/SVGFEDropShadowElement.cpp

Index: Source/core/svg/SVGFEDropShadowElement.cpp
diff --git a/Source/core/svg/SVGFEDropShadowElement.cpp b/Source/core/svg/SVGFEDropShadowElement.cpp
index 932e30e67e55f11db9e4917e2381d78b8880c3f5..24775e128e36b86bfa9db5dbe66bbbbb282017b1 100644
--- a/Source/core/svg/SVGFEDropShadowElement.cpp
+++ b/Source/core/svg/SVGFEDropShadowElement.cpp
@@ -80,9 +80,6 @@ PassRefPtrWillBeRawPtr<FilterEffect> SVGFEDropShadowElement::build(SVGFilterBuil
     if (!layoutObject)
         return nullptr;
 
-    if (stdDeviationX()->currentValue()->value() < 0 || stdDeviationY()->currentValue()->value() < 0)
-        return nullptr;
-
     ASSERT(layoutObject->style());
     const SVGComputedStyle& svgStyle = layoutObject->style()->svgStyle();
 
@@ -93,7 +90,10 @@ PassRefPtrWillBeRawPtr<FilterEffect> SVGFEDropShadowElement::build(SVGFilterBuil
     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();
 }