Make text track and cue wrapper objects dependent on their media element.

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 65 matching lines @@
 TextTrack* TextTrackCue::track() const
 {
     return m_track;
 }
 
 void TextTrackCue::setTrack(TextTrack* track)
 {
     m_track = track;
 }
 
+Node* TextTrackCue::owner() const
+{
+    return m_track ? m_track->owner() : 0;
+}
+
 void TextTrackCue::setId(const AtomicString& id)
 {
     if (m_id == id)
         return;
 
     cueWillChange();
     m_id = id;
     cueDidChange();
 }
 
@@ skipping 72 matching lines @@
     if (!active)
         removeDisplayTree();
 }
 
 const AtomicString& TextTrackCue::interfaceName() const
 {
     return EventTargetNames::TextTrackCue;
 }
 
 } // namespace WebCore