MSE: Implement TrackDefaultList object

Source/modules/mediasource/TrackDefaultList.h

+// 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.
+
+#ifndef TrackDefaultList_h
+#define TrackDefaultList_h
+
+#include "bindings/core/v8/ScriptWrappable.h"
+#include "modules/mediasource/TrackDefault.h"
+#include "platform/heap/Handle.h"
+
+namespace blink {
+
+class ExceptionState;
+
+class TrackDefaultList final : public GarbageCollected<TrackDefaultList>, public ScriptWrappable {
+    DEFINE_WRAPPERTYPEINFO();
+public:
+    static TrackDefaultList* create(); // Creates an empty TrackDefaultList.
+
+    static TrackDefaultList* create(const HeapVector<Member<TrackDefault>>&, ExceptionState&);
+
+    // Implement the IDL
+    unsigned length() const { return m_trackDefaults.size(); }
+    TrackDefault* item(unsigned) const;
+
+    void trace(Visitor*);
+
+private:
+    TrackDefaultList();
+
+    explicit TrackDefaultList(const HeapVector<Member<TrackDefault>>&);
+
+    const HeapVector<Member<TrackDefault>> m_trackDefaults;
+};
+
+} // namespace blink
+
+#endif // TrackDefaultList_h