Use nullptr_t for RefPtr, PassRefPtr and RawPtr.

Source/core/svg/SVGFEColorMatrixElement.cpp

Index: Source/core/svg/SVGFEColorMatrixElement.cpp
diff --git a/Source/core/svg/SVGFEColorMatrixElement.cpp b/Source/core/svg/SVGFEColorMatrixElement.cpp
index 7131ede1c19fa365e16686531a2cbabe51929550..d2d0108126aecea414c97c3e35372a68504379cd 100644
--- a/Source/core/svg/SVGFEColorMatrixElement.cpp
+++ b/Source/core/svg/SVGFEColorMatrixElement.cpp
@@ -138,7 +138,7 @@ PassRefPtr<FilterEffect> SVGFEColorMatrixElement::build(SVGFilterBuilder* filter
     FilterEffect* input1 = filterBuilder->getEffectById(AtomicString(m_in1->currentValue()->value()));
 
     if (!input1)
-        return 0;
+        return nullptr;
 
     Vector<float> filterValues;
     ColorMatrixType filterType = m_type->currentValue()->enumValue();
@@ -166,7 +166,7 @@ PassRefPtr<FilterEffect> SVGFEColorMatrixElement::build(SVGFilterBuilder* filter
         if ((filterType == FECOLORMATRIX_TYPE_MATRIX && size != 20)
             || (filterType == FECOLORMATRIX_TYPE_HUEROTATE && size != 1)
             || (filterType == FECOLORMATRIX_TYPE_SATURATE && size != 1))
-            return 0;
+            return nullptr;
 
         filterValues = values->toFloatVector();
     }