Use nullptr_t for RefPtr, PassRefPtr and RawPtr.

Source/core/editing/TextCheckingHelper.cpp

 /*
  * Copyright (C) 2006, 2007 Apple Inc. All rights reserved.
  * Copyright (C) 2008 Nokia Corporation and/or its subsidiary(-ies)
  *
  * 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 119 matching lines @@
 void TextCheckingParagraph::expandRangeToNextEnd()
 {
     ASSERT(m_checkingRange);
     setEnd(paragraphRange().get(), endOfParagraph(startOfNextParagraph(paragraphRange()->startPosition())));
     invalidateParagraphRangeValues();
 }
 
 void TextCheckingParagraph::invalidateParagraphRangeValues()
 {
     m_checkingStart = m_checkingEnd = -1;
-    m_offsetAsRange = 0;
+    m_offsetAsRange = nullptr;
     m_text = String();
 }
 
 int TextCheckingParagraph::rangeLength() const
 {
     ASSERT(m_checkingRange);
     return TextIterator::rangeLength(paragraphRange().get());
 }
 
 PassRefPtr<Range> TextCheckingParagraph::paragraphRange() const
@@ skipping 418 matching lines @@
         return false;
 
     const Settings* settings = frame->settings();
     if (!settings)
         return false;
 
     return settings->unifiedTextCheckerEnabled();
 }
 
 }