Use nullptr_t for RefPtr, PassRefPtr and RawPtr.

Source/wtf/text/StringBuilder.h

 /*
  * Copyright (C) 2009, 2010, 2012, 2013 Apple Inc. All rights reserved.
  * Copyright (C) 2012 Google 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 246 matching lines @@
         ASSERT(m_buffer);
         return m_buffer->characters16();
     }
 
     bool is8Bit() const { return m_is8Bit; }
 
     void clear()
     {
         m_length = 0;
         m_string = String();
-        m_buffer = 0;
+        m_buffer = nullptr;
         m_bufferCharacters8 = 0;
         m_is8Bit = true;
     }
 
     void swap(StringBuilder& stringBuilder)
     {
         std::swap(m_length, stringBuilder.m_length);
         m_string.swap(stringBuilder.m_string);
         m_buffer.swap(stringBuilder.m_buffer);
         std::swap(m_is8Bit, stringBuilder.m_is8Bit);
@@ skipping 113 matching lines @@
 inline bool operator==(const StringBuilder& a, const String& b) { return equal(a, b); }
 inline bool operator!=(const StringBuilder& a, const String& b) { return !equal(a, b); }
 inline bool operator==(const String& a, const StringBuilder& b) { return equal(b, a); }
 inline bool operator!=(const String& a, const StringBuilder& b) { return !equal(b, a); }
 
 } // namespace WTF
 
 using WTF::StringBuilder;
 
 #endif // StringBuilder_h