Use nullptr_t for RefPtr, PassRefPtr and RawPtr.

Source/core/html/HTMLMediaElement.h

 /*
  * Copyright (C) 2007, 2008, 2009, 2010, 2011, 2012, 2013 Apple 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
  *    notice, this list of conditions and the following disclaimer in the
@@ skipping 186 matching lines @@
 
     virtual void mediaPlayerDidAddTrack(blink::WebInbandTextTrack*) OVERRIDE FINAL;
     virtual void mediaPlayerDidRemoveTrack(blink::WebInbandTextTrack*) OVERRIDE FINAL;
     // FIXME: Remove this when WebMediaPlayerClientImpl::loadInternal does not depend on it.
     virtual KURL mediaPlayerPosterURL() OVERRIDE { return KURL(); }
 
     struct TrackGroup {
         enum GroupKind { CaptionsAndSubtitles, Description, Chapter, Metadata, Other };
 
         TrackGroup(GroupKind kind)
-            : visibleTrack(0)
-            , defaultTrack(0)
+            : visibleTrack(nullptr)
+            , defaultTrack(nullptr)
             , kind(kind)
             , hasSrcLang(false)
         {
         }
 
         Vector<RefPtr<TextTrack> > tracks;
         RefPtr<TextTrack> visibleTrack;
         RefPtr<TextTrack> defaultTrack;
         GroupKind kind;
         bool hasSrcLang;
@@ skipping 376 matching lines @@
 inline bool isHTMLMediaElement(const Node& node)
 {
     return node.isElementNode() && toElement(node).isMediaElement();
 }
 
 DEFINE_NODE_TYPE_CASTS_WITH_FUNCTION(HTMLMediaElement);
 
 } //namespace
 
 #endif