Use nullptr_t for RefPtr, PassRefPtr and RawPtr.

Source/core/svg/SVGFETurbulenceElement.cpp

Index: Source/core/svg/SVGFETurbulenceElement.cpp
diff --git a/Source/core/svg/SVGFETurbulenceElement.cpp b/Source/core/svg/SVGFETurbulenceElement.cpp
index 7cd8bb10513389a8bb35bc057924720c1ff3f35e..043669b078e4e3e525075f1f948a636608a5aa35 100644
--- a/Source/core/svg/SVGFETurbulenceElement.cpp
+++ b/Source/core/svg/SVGFETurbulenceElement.cpp
@@ -162,7 +162,7 @@ void SVGFETurbulenceElement::svgAttributeChanged(const QualifiedName& attrName)
 PassRefPtr<FilterEffect> SVGFETurbulenceElement::build(SVGFilterBuilder*, Filter* filter)
 {
     if (baseFrequencyX()->currentValue()->value() < 0 || baseFrequencyY()->currentValue()->value() < 0)
-        return 0;
+        return nullptr;
     return FETurbulence::create(filter, m_type->currentValue()->enumValue(), baseFrequencyX()->currentValue()->value(), baseFrequencyY()->currentValue()->value(), m_numOctaves->currentValue()->value(), m_seed->currentValue()->value(), m_stitchTiles->currentValue()->enumValue() == SVG_STITCHTYPE_STITCH);
 }