Use nullptr_t for RefPtr, PassRefPtr and RawPtr.

Source/core/svg/graphics/filters/SVGFilterBuilder.cpp

 /*
  * Copyright (C) 2009 Dirk Schulze <krit@webkit.org>
  *
  * This library is free software; you can redistribute it and/or
  * modify it under the terms of the GNU Library General Public
  * License as published by the Free Software Foundation; either
  * version 2 of the License, or (at your option) any later version.
  *
  * This library is distributed in the hope that it will be useful,
  * but WITHOUT ANY WARRANTY; without even the implied warranty of
@@ skipping 62 matching lines @@
     unsigned numberOfInputEffects = effect->inputEffects().size();
 
     // It is not possible to add the same value to a set twice.
     for (unsigned i = 0; i < numberOfInputEffects; ++i)
         effectReferences(effect->inputEffect(i)).add(effect.get());
     m_effectRenderer.add(object, effect.get());
 }
 
 void SVGFilterBuilder::clearEffects()
 {
-    m_lastEffect = 0;
+    m_lastEffect = nullptr;
     m_namedEffects.clear();
     m_effectReferences.clear();
     m_effectRenderer.clear();
     addBuiltinEffects();
 }
 
 void SVGFilterBuilder::clearResultsRecursive(FilterEffect* effect)
 {
     if (!effect->hasResult())
         return;
 
     effect->clearResult();
 
     HashSet<FilterEffect*>& effectReferences = this->effectReferences(effect);
     HashSet<FilterEffect*>::iterator end = effectReferences.end();
     for (HashSet<FilterEffect*>::iterator it = effectReferences.begin(); it != end; ++it)
          clearResultsRecursive(*it);
 }
 
 } // namespace WebCore