Use nullptr_t for RefPtr, PassRefPtr and RawPtr.

Source/platform/fonts/FontDataCache.cpp

 /*
  * Copyright (C) 2013 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:
  *
  *     * Redistributions of source code must retain the above copyright
  * notice, this list of conditions and the following disclaimer.
  *     * Redistributions in binary form must reproduce the above
@@ skipping 30 matching lines @@
 const unsigned cMaxInactiveFontData = 250;
 const unsigned cTargetInactiveFontData = 200;
 #else
 const unsigned cMaxInactiveFontData = 225;
 const unsigned cTargetInactiveFontData = 200;
 #endif
 
 PassRefPtr<SimpleFontData> FontDataCache::get(const FontPlatformData* platformData, ShouldRetain shouldRetain)
 {
     if (!platformData)
-        return 0;
+        return nullptr;
 
     Cache::iterator result = m_cache.find(*platformData);
     if (result == m_cache.end()) {
         pair<RefPtr<SimpleFontData>, unsigned> newValue(SimpleFontData::create(*platformData), shouldRetain == Retain ? 1 : 0);
         m_cache.set(*platformData, newValue);
         if (shouldRetain == DoNotRetain)
             m_inactiveFontData.add(newValue.first);
         return newValue.first.release();
     }
 
@@ skipping 84 matching lines @@
     bool didWork = fontDataToDelete.size();
 
     fontDataToDelete.clear();
 
     isPurging = false;
 
     return didWork;
 }
 
 }