Use nullptr_t for RefPtr, PassRefPtr and RawPtr.

Source/core/events/MutationEvent.h

Index: Source/core/events/MutationEvent.h
diff --git a/Source/core/events/MutationEvent.h b/Source/core/events/MutationEvent.h
index e2e9f56ac140308bf09e819aa5e1ac09b15b82b0..7385653718e584dd14d84a131044366eaa88aa79 100644
--- a/Source/core/events/MutationEvent.h
+++ b/Source/core/events/MutationEvent.h
@@ -44,7 +44,7 @@ namespace WebCore {
             return adoptRef(new MutationEvent);
         }
 
-        static PassRefPtr<MutationEvent> create(const AtomicString& type, bool canBubble, PassRefPtr<Node> relatedNode = 0,
+        static PassRefPtr<MutationEvent> create(const AtomicString& type, bool canBubble, PassRefPtr<Node> relatedNode = nullptr,
             const String& prevValue = String(), const String& newValue = String(), const String& attrName = String(), unsigned short attrChange = 0)
         {
             return adoptRef(new MutationEvent(type, canBubble, false, relatedNode, prevValue, newValue, attrName, attrChange));