Use nullptr_t for RefPtr, PassRefPtr and RawPtr.

Source/core/svg/SVGFEGaussianBlurElement.cpp

Index: Source/core/svg/SVGFEGaussianBlurElement.cpp
diff --git a/Source/core/svg/SVGFEGaussianBlurElement.cpp b/Source/core/svg/SVGFEGaussianBlurElement.cpp
index 35b3892ec2588800a6f48d062d315e3875c15086..86982750ffac2a5f49b8b9b415f5f6ae8678caf1 100644
--- a/Source/core/svg/SVGFEGaussianBlurElement.cpp
+++ b/Source/core/svg/SVGFEGaussianBlurElement.cpp
@@ -111,10 +111,10 @@ PassRefPtr<FilterEffect> SVGFEGaussianBlurElement::build(SVGFilterBuilder* filte
     FilterEffect* input1 = filterBuilder->getEffectById(AtomicString(m_in1->currentValue()->value()));
 
     if (!input1)
-        return 0;
+        return nullptr;
 
     if (stdDeviationX()->currentValue()->value() < 0 || stdDeviationY()->currentValue()->value() < 0)
-        return 0;
+        return nullptr;
 
     RefPtr<FilterEffect> effect = FEGaussianBlur::create(filter, stdDeviationX()->currentValue()->value(), stdDeviationY()->currentValue()->value());
     effect->inputEffects().append(input1);