Use nullptr_t for RefPtr, PassRefPtr and RawPtr.

Source/core/loader/FrameLoader.h

 /*
  * Copyright (C) 2006, 2007, 2008, 2009, 2011 Apple Inc. All rights reserved.
  * Copyright (C) 2008, 2009 Torch Mobile Inc. All rights reserved. (http://www.torchmobile.com/)
  * Copyright (C) Research In Motion Limited 2009. All rights reserved.
  * Copyright (C) 2011 Google 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:
  *
@@ skipping 210 matching lines @@
 
     // Calls continueLoadAfterNavigationPolicy
     void loadWithNavigationAction(const NavigationAction&, FrameLoadType, PassRefPtr<FormState>,
         const SubstituteData&, ClientRedirectPolicy = NotClientRedirect, const AtomicString& overrideEncoding = nullAtom);
 
     void detachFromParent();
     void detachChildren();
     void closeAndRemoveChild(Frame*);
     void detachClient();
 
-    void setHistoryItemStateForCommit(HistoryCommitType, bool isPushOrReplaceState = false, PassRefPtr<SerializedScriptValue> = 0);
+    void setHistoryItemStateForCommit(HistoryCommitType, bool isPushOrReplaceState = false, PassRefPtr<SerializedScriptValue> = nullptr);
 
     void loadInSameDocument(const KURL&, PassRefPtr<SerializedScriptValue> stateObject, UpdateBackForwardListPolicy, ClientRedirectPolicy);
 
     void scheduleCheckCompleted();
     void startCheckCompleteTimer();
 
     Frame* m_frame;
     FrameLoaderClient* m_client;
 
     // FIXME: These should be OwnPtr<T> to reduce build times and simplify
@@ skipping 33 matching lines @@
 
     bool m_didAccessInitialDocument;
     Timer<FrameLoader> m_didAccessInitialDocumentTimer;
 
     SandboxFlags m_forcedSandboxFlags;
 };
 
 } // namespace WebCore
 
 #endif // FrameLoader_h