Use nullptr_t for RefPtr, PassRefPtr and RawPtr.

Source/platform/graphics/filters/FilterOperation.h

 /*
  * Copyright (C) 2011 Apple Inc. All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions
  * are met:
  * 1. Redistributions of source code must retain the above copyright
  *    notice, this list of conditions and the following disclaimer.
  * 2. Redistributions in binary form must reproduce the above copyright
  *    notice, this list of conditions and the following disclaimer in the
@@ skipping 115 matching lines @@
     const String& url() const { return m_url; }
     const AtomicString& fragment() const { return m_fragment; }
 
     ReferenceFilter* filter() const { return m_filter.get(); }
     void setFilter(PassRefPtr<ReferenceFilter> filter) { m_filter = filter; }
 
 private:
     virtual PassRefPtr<FilterOperation> blend(const FilterOperation* from, double progress) const OVERRIDE
     {
         ASSERT_NOT_REACHED();
-        return 0;
+        return nullptr;
     }
 
     virtual bool operator==(const FilterOperation& o) const OVERRIDE
     {
         if (!isSameType(o))
             return false;
         const ReferenceFilterOperation* other = static_cast<const ReferenceFilterOperation*>(&o);
         return m_url == other->m_url;
     }
 
@@ skipping 163 matching lines @@
     int m_stdDeviation;
     Color m_color;
 };
 
 DEFINE_FILTER_OPERATION_TYPE_CASTS(DropShadowFilterOperation, DROP_SHADOW);
 
 } // namespace WebCore
 
 
 #endif // FilterOperation_h