Implement AudioTrack, AudioTrackList, VideoTrack, and VideoTrackList

Source/core/html/track/VideoTrackList.idl

Index: Source/core/html/track/VideoTrackList.idl
diff --git a/Source/core/html/track/VideoTrackList.idl b/Source/core/html/track/VideoTrackList.idl
new file mode 100644
index 0000000000000000000000000000000000000000..f766335064913901c9d0ff1e3dab43c068001120
--- /dev/null
+++ b/Source/core/html/track/VideoTrackList.idl
@@ -0,0 +1,17 @@
+// Copyright 2014 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+[
+    RuntimeEnabled=AudioVideoTracks,
+    SetWrapperReferenceFrom=owner,
+] interface VideoTrackList : EventTarget {
+  readonly attribute unsigned long length;
+  getter VideoTrack (unsigned long index);
+  VideoTrack? getTrackById(DOMString id);
+  readonly attribute long selectedIndex;
+
+  attribute EventHandler onchange;
+  attribute EventHandler onaddtrack;
+  attribute EventHandler onremovetrack;
+};