MSE: Implement TrackDefault object

Source/modules/mediasource/TrackDefault.idl

+// 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.
+
+// Per 11 Nov 2014 Editor's Draft
+// https://dvcs.w3.org/hg/html-media/raw-file/tip/media-source/media-source.html#idl-def-TrackDefault
+
+enum TrackDefaultType { "audio", "video", "text" };
+
+[
+    Constructor(TrackDefaultType type, DOMString language, DOMString label, sequence<DOMString> kinds, optional DOMString byteStreamTrackID = ""),
+    RaisesException=Constructor,
+    GarbageCollected,
+    RuntimeEnabled=MediaSourceExperimental,
+    TypeChecking=Interface,

[sof, 2014/11/13 20:45:42]

Is this needed for anything here?

[wolenetz, 2014/11/13 22:56:40]

I had thought this enforced the constructor's |type| parameter to be a member of
enum TrackDefaultType and |kinds| to be a sequence (or otherwise emit
TypeError).

I was mistaken, these checks are still in generated code without this line in
idl.
Done.

+] interface TrackDefault {
+  readonly attribute TrackDefaultType type;

[sof, 2014/11/13 20:45:42]

nit: 4-space indented?

[wolenetz, 2014/11/13 22:56:40]

Done. Thanks.

+  readonly attribute DOMString byteStreamTrackID;
+  readonly attribute DOMString language;
+  readonly attribute DOMString label;
+  readonly attribute DOMString[] kinds;
+};