Oilpan: add transition types to track interface objects.

Source/core/html/track/TextTrackCue.cpp

 /*
  * Copyright (C) 2011 Google Inc.  All rights reserved.
  * Copyright (C) 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:
  *
  *     * Redistributions of source code must retain the above copyright
  * notice, this list of conditions and the following disclaimer.
@@ skipping 37 matching lines @@
         exceptionState.throwTypeError(ExceptionMessages::notAFiniteNumber(value));
         return true;
     }
     return false;
 }
 
 TextTrackCue::TextTrackCue(double start, double end)
     : m_startTime(start)
     , m_endTime(end)
     , m_cueIndex(invalidCueIndex)
-    , m_track(0)
+    , m_track(nullptr)
     , m_isActive(false)
     , m_pauseOnExit(false)
 {
 }
 
 void TextTrackCue::cueWillChange()
 {
     if (m_track)
         m_track->cueWillChange(this);
 }
@@ skipping 103 matching lines @@
     // Remove the display tree as soon as the cue becomes inactive.
     if (!active)
         removeDisplayTree();
 }
 
 const AtomicString& TextTrackCue::interfaceName() const
 {
     return EventTargetNames::TextTrackCue;
 }
 
+void TextTrackCue::trace(Visitor* visitor)
+{
+    visitor->trace(m_track);
+}
+
 } // namespace WebCore