Initial implementation of AudioTrack, AudioTrackList, VideoTrack, and VideoTrackList.

Source/core/html/track/TrackBase.h

Index: Source/core/html/track/TrackBase.h
diff --git a/Source/core/html/track/TrackBase.h b/Source/core/html/track/TrackBase.h
index b291c68db363fd0a7b2e59c5c97e2c86a39aa651..ec159064cfb5dda58afb9201dfd3b6982e8d878c 100644
--- a/Source/core/html/track/TrackBase.h
+++ b/Source/core/html/track/TrackBase.h
@@ -31,6 +31,8 @@
 
 namespace WebCore {
 
+class HTMLMediaElement;
+
 class TrackBase : public RefCounted<TrackBase> {
 public:
     virtual ~TrackBase();
@@ -50,6 +52,9 @@ public:
     AtomicString id() const { return m_id; }
     void setId(const AtomicString& id) { m_id = id; }
 
+    void setMediaElement(HTMLMediaElement* mediaElement) { m_mediaElement = mediaElement; }
+    HTMLMediaElement* mediaElement() const { return m_mediaElement; }
+
 protected:
     TrackBase(Type, const AtomicString& label, const AtomicString& language, const AtomicString& id);
 
@@ -62,6 +67,7 @@ private:
     AtomicString m_label;
     AtomicString m_language;
     AtomicString m_id;
+    HTMLMediaElement* m_mediaElement;

[philipj_slow, 2014/03/13 10:00:04]

This is used to notify the media element of changes and fire events. TextTrack
solves this by having an m_trackList owner. If TrackBase and TrackBaseList are
both parameterized Could this not be a TrackBaseList<SomethingTrack> instead? It
seems more sensible layering-wise for the track list to fire fire the event on
itself, and the media element to take care of notifying the backend.

[acolwell GONE FROM CHROMIUM, 2014/03/18 22:02:15]

I had the lists fire their own events in a previous iteration of this CL, but it
complicates things for a future CL where I add these list types to the
SourceBuffer. It is possible to select a track from either the lists on the
HTMLMediaElement OR the ones on the SourceBuffer. I decided to have the tracks
notify the HTMLMediaElement first to allow consistent event firing behavior when
both the SourceBuffer and HTMLMediaElement track lists need to be updated and
fire events.

[philipj_slow, 2014/03/20 16:17:40]

OK, it's related to the "FIXME: Add call on m_mediaSource to notify it of track
changes once the SourceBuffer.audioTracks attribute is added." The layering
there would be similar, would it work to have a TrackListListener interface
which both HTMLMediaElement and SourceBuffer implement?

I can't see the end result clearly before me, so we can leave this as is if you
think it'll be fine.

 };
 
 } // namespace WebCore