Use nullptr_t for RefPtr, PassRefPtr and RawPtr.

Source/core/dom/TreeScope.cpp

 /*
  * Copyright (C) 2011 Google Inc. All Rights Reserved.
  * Copyright (C) 2012 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
@@ skipping 66 matching lines @@
     m_rootNode.setTreeScope(this);
 }
 
 TreeScope::~TreeScope()
 {
     ASSERT(!m_guardRefCount);
     m_rootNode.setTreeScope(0);
 
     if (m_selection) {
         m_selection->clearTreeScope();
-        m_selection = 0;
+        m_selection = nullptr;
     }
 
     if (m_parentTreeScope)
         m_parentTreeScope->guardDeref();
 }
 
 TreeScope* TreeScope::olderShadowRootOrParentTreeScope() const
 {
     if (rootNode().isShadowRoot()) {
         if (ShadowRoot* olderShadowRoot = toShadowRoot(rootNode()).olderShadowRoot())
@@ skipping 395 matching lines @@
     for (Element* element = ElementTraversal::firstWithin(rootNode()); element; element = ElementTraversal::nextIncludingPseudo(*element)) {
         for (ShadowRoot* root = element->youngestShadowRoot(); root; root = root->olderShadowRoot())
             root->setNeedsStyleRecalcForViewportUnits();
         RenderStyle* style = element->renderStyle();
         if (style && style->hasViewportUnits())
             element->setNeedsStyleRecalc(LocalStyleChange);
     }
 }
 
 } // namespace WebCore