Use nullptr_t for RefPtr, PassRefPtr and RawPtr.

Source/core/editing/TextIterator.cpp

 /*
  * Copyright (C) 2004, 2005, 2006, 2007, 2008, 2009, 2010, 2012 Apple Inc. All rights reserved.
  * Copyright (C) 2005 Alexey Proskuryakov.
  *
  * 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 1110 matching lines @@
             m_positionEndOffset += index;
             m_positionOffsetBaseNode = 0;
         }
         return Range::create(m_positionNode->document(), m_positionNode, m_positionStartOffset, m_positionNode, m_positionEndOffset);
     }
 
     // otherwise, return the end of the overall range we were given
     if (m_endContainer)
         return Range::create(m_endContainer->document(), m_endContainer, m_endOffset, m_endContainer, m_endOffset);
 
-    return 0;
+    return nullptr;
 }
 
 Node* TextIterator::node() const
 {
     RefPtr<Range> textRange = range();
     if (!textRange)
         return 0;
 
     Node* node = textRange->startContainer();
     if (!node)
@@ skipping 939 matching lines @@
         if (!matchLength)
             return collapsedToBoundary(range, !(options & Backwards));
     }
 
     // Then, find the document position of the start and the end of the text.
     CharacterIterator computeRangeIterator(range, TextIteratorEntersTextControls | TextIteratorEntersAuthorShadowRoots);
     return characterSubrange(computeRangeIterator, matchStart, matchLength);
 }
 
 }