Use nullptr_t for RefPtr, PassRefPtr and RawPtr.

Source/core/html/HTMLSelectElement.cpp

 /*
  * Copyright (C) 2010 Nokia Corporation and/or its subsidiary(-ies).
  * Copyright (C) 1999 Lars Knoll (knoll@kde.org)
  *           (C) 1999 Antti Koivisto (koivisto@kde.org)
  *           (C) 2001 Dirk Mueller (mueller@kde.org)
  * Copyright (C) 2004, 2005, 2006, 2007, 2009, 2010, 2011 Apple Inc. All rights reserved.
  *           (C) 2006 Alexey Proskuryakov (ap@nypop.com)
  * Copyright (C) 2010 Google Inc. All rights reserved.
  * Copyright (C) 2009 Torch Mobile Inc. All rights reserved. (http://www.torchmobile.com/)
  *
@@ skipping 391 matching lines @@
 Element* HTMLSelectElement::item(unsigned index)
 {
     return options()->item(index);
 }
 
 void HTMLSelectElement::setOption(unsigned index, HTMLOptionElement* option, ExceptionState& exceptionState)
 {
     if (index > maxSelectItems - 1)
         index = maxSelectItems - 1;
     int diff = index - length();
-    RefPtr<HTMLElement> before = 0;
+    RefPtr<HTMLElement> before = nullptr;
     // Out of array bounds? First insert empty dummies.
     if (diff > 0) {
         setLength(index, exceptionState);
         // Replace an existing entry?
     } else if (diff < 0) {
         before = toHTMLElement(options()->item(index+1));
         remove(index);
     }
     // Finally add the new element.
     if (!exceptionState.hadException()) {
@@ skipping 1146 matching lines @@
 {
     return true;
 }
 
 bool HTMLSelectElement::supportsAutofocus() const
 {
     return true;
 }
 
 } // namespace