Move code that applies to audio and video tracks into TrackBase.

Source/core/html/track/TextTrackList.cpp

 /*
  * Copyright (C) 2011, 2012 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 174 matching lines @@
         m_elementTracks.insert(index, track);
     } else if (track->trackType() == TextTrack::InBand) {
         // Insert tracks added for in-band in the media file order.
         size_t index = static_cast<InbandTextTrack*>(track.get())->inbandTrackIndex();
         m_inbandTracks.insert(index, track);
     } else
         ASSERT_NOT_REACHED();
 
     invalidateTrackIndexesAfterTrack(track.get());
 
-    ASSERT(!track->mediaElement() || track->mediaElement() == m_owner);
-    track->setMediaElement(m_owner);
+    ASSERT(!track->trackList());
+    track->setTrackList(this);
 
     scheduleAddTrackEvent(track.release());
 }
 
 void TextTrackList::remove(TextTrack* track)
 {
     Vector<RefPtr<TextTrack> >* tracks = 0;
     RefPtr<InbandTextTrack> inbandTrack;
 
     if (track->trackType() == TextTrack::TrackElement) {
         tracks = &m_elementTracks;
     } else if (track->trackType() == TextTrack::AddTrack) {
         tracks = &m_addTrackTracks;
     } else if (track->trackType() == TextTrack::InBand) {
         tracks = &m_inbandTracks;
         inbandTrack = static_cast<InbandTextTrack*>(track);
     } else {
         ASSERT_NOT_REACHED();
     }
 
     size_t index = tracks->find(track);
     if (index == kNotFound)
         return;
 
     invalidateTrackIndexesAfterTrack(track);
 
-    ASSERT(track->mediaElement() == m_owner);
-    track->setMediaElement(0);
+    ASSERT(track->trackList() == this);
+    track->setTrackList(0);
 
     tracks->remove(index);
 
     if (inbandTrack)
         inbandTrack->trackRemoved();
 
     scheduleRemoveTrackEvent(track);
 }
 
 bool TextTrackList::contains(TextTrack* track) const
@@ skipping 72 matching lines @@
     // interface, with the track attribute initialized to the text track's
     // TextTrack object, at the media element's textTracks attribute's
     // TextTrackList object.
     scheduleTrackEvent(EventTypeNames::removetrack, track);
 }
 
 Node* TextTrackList::owner() const
 {
     return m_owner;
 }