Use nullptr_t for RefPtr, PassRefPtr and RawPtr.

Source/core/html/HTMLElement.cpp

 /*
  * Copyright (C) 1999 Lars Knoll (knoll@kde.org)
  *           (C) 1999 Antti Koivisto (koivisto@kde.org)
  * Copyright (C) 2004, 2005, 2006, 2007, 2008 Apple Inc. All rights reserved.
  * Copyright (C) 2009 Torch Mobile Inc. All rights reserved. (http://www.torchmobile.com/)
  * Copyright (C) 2011 Motorola Mobility. All rights reserved.
  *
  * 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
@@ skipping 322 matching lines @@
 
         // Find next line break.
         for (i = start; i < length; i++) {
           c = text[i];
           if (c == '\r' || c == '\n')
               break;
         }
 
         fragment->appendChild(Text::create(document(), text.substring(start, i - start)), exceptionState);
         if (exceptionState.hadException())
-            return 0;
+            return nullptr;
 
         if (c == '\r' || c == '\n') {
             fragment->appendChild(HTMLBRElement::create(document()), exceptionState);
             if (exceptionState.hadException())
-                return 0;
+                return nullptr;
             // Make sure \r\n doesn't result in two line breaks.
             if (c == '\r' && i + 1 < length && text[i + 1] == '\n')
                 i++;
         }
 
         start = i + 1; // Character after line break.
     }
 
     return fragment;
 }
@@ skipping 591 matching lines @@
 #ifndef NDEBUG
 
 // For use in the debugger
 void dumpInnerHTML(WebCore::HTMLElement*);
 
 void dumpInnerHTML(WebCore::HTMLElement* element)
 {
     printf("%s\n", element->innerHTML().ascii().data());
 }
 #endif