Use nullptr_t for RefPtr, PassRefPtr and RawPtr.

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 5d219c5054ddb135f56b9ca2c15346346460d3ff..271f3a42f14cef0a7ad229d6cb814bd9a9ec99d4 100644
--- a/Source/core/svg/SVGFEDropShadowElement.cpp
+++ b/Source/core/svg/SVGFEDropShadowElement.cpp
@@ -123,10 +123,10 @@ PassRefPtr<FilterEffect> SVGFEDropShadowElement::build(SVGFilterBuilder* filterB
 {
     RenderObject* renderer = this->renderer();
     if (!renderer)
-        return 0;
+        return nullptr;
 
     if (stdDeviationX()->currentValue()->value() < 0 || stdDeviationY()->currentValue()->value() < 0)
-        return 0;
+        return nullptr;
 
     ASSERT(renderer->style());
     const SVGRenderStyle* svgStyle = renderer->style()->svgStyle();
@@ -136,7 +136,7 @@ PassRefPtr<FilterEffect> SVGFEDropShadowElement::build(SVGFilterBuilder* filterB
 
     FilterEffect* input1 = filterBuilder->getEffectById(AtomicString(m_in1->currentValue()->value()));
     if (!input1)
-        return 0;
+        return nullptr;
 
     RefPtr<FilterEffect> effect = FEDropShadow::create(filter, stdDeviationX()->currentValue()->value(), stdDeviationY()->currentValue()->value(), m_dx->currentValue()->value(), m_dy->currentValue()->value(), color, opacity);
     effect->inputEffects().append(input1);