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

Source/core/html/track/TextTrackList.cpp

Index: Source/core/html/track/TextTrackList.cpp
diff --git a/Source/core/html/track/TextTrackList.cpp b/Source/core/html/track/TextTrackList.cpp
index 0d00ba33fee5220d99c603292f4bc7a5808b24e2..f3a7c3be63352dab6b635f21088413d2b32c0221 100644
--- a/Source/core/html/track/TextTrackList.cpp
+++ b/Source/core/html/track/TextTrackList.cpp
@@ -192,8 +192,8 @@ void TextTrackList::append(PassRefPtr<TextTrack> prpTrack)
 
     invalidateTrackIndexesAfterTrack(track.get());
 
-    ASSERT(!track->mediaElement() || track->mediaElement() == m_owner);
-    track->setMediaElement(m_owner);
+    ASSERT(!track->trackList() || track->trackList() == this);

[acolwell GONE FROM CHROMIUM, 2013/12/06 01:35:54]

"track->trackList() == this" seems a little weird. What is the case where the
track list is set already and append() is called? If the track is already part
of this list, why would we allow it to be added again?

+    track->setTrackList(this);
 
     scheduleAddTrackEvent(track.release());
 }
@@ -220,8 +220,8 @@ void TextTrackList::remove(TextTrack* track)
 
     invalidateTrackIndexesAfterTrack(track);
 
-    ASSERT(track->mediaElement() == m_owner);
-    track->setMediaElement(0);
+    ASSERT(track->trackList() == this);
+    track->setTrackList(0);
 
     tracks->remove(index);