Use nullptr_t for RefPtr, PassRefPtr and RawPtr.

Source/core/page/FrameTree.cpp

 /*
  * Copyright (C) Research In Motion Limited 2010. All rights reserved.
  * Copyright (C) 2006 Apple Computer, Inc.
  *
  * 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,
@@ skipping 33 matching lines @@
 FrameTree::FrameTree(Frame* thisFrame)
     : m_thisFrame(thisFrame)
     , m_scopedChildCount(invalidChildCount)
 {
 }
 
 FrameTree::~FrameTree()
 {
     // FIXME: Why is this here? Doesn't this parallel what we already do in ~Frame?
     for (Frame* child = firstChild(); child; child = child->tree().nextSibling())
-        child->setView(0);
+        child->setView(nullptr);
 }
 
 void FrameTree::setName(const AtomicString& name)
 {
     m_name = name;
     if (!parent()) {
         m_uniqueName = name;
         return;
     }
     m_uniqueName = AtomicString(); // Remove our old frame name so it's not considered in uniqueChildName.
@@ skipping 330 matching lines @@
 {
     if (!frame) {
         printf("Null input frame\n");
         return;
     }
 
     printFrames(frame->tree().top(), frame, 0);
 }
 
 #endif