TrackEvent.track should be (VideoTrack or AudioTrack or TextTrack)?

Source/core/html/track/TrackEvent.idl

Index: Source/core/html/track/TrackEvent.idl
diff --git a/Source/core/html/track/TrackEvent.idl b/Source/core/html/track/TrackEvent.idl
index 38ad03dcdd86414d1802890bc9275901dcc3c088..22d7ece8acb60b8b31c522cf92a345a0f9baf1c7 100644
--- a/Source/core/html/track/TrackEvent.idl
+++ b/Source/core/html/track/TrackEvent.idl
@@ -23,8 +23,10 @@
  * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
  */
 
+// https://html.spec.whatwg.org/multipage/embedded-content.html#the-trackevent-interface
+
 [
     EventConstructor,
 ] interface TrackEvent : Event {
-    [InitializedByEventConstructor, Custom=Getter] readonly attribute object track;
-};
+    [InitializedByEventConstructor] readonly attribute (VideoTrack or AudioTrack or TextTrack)? track;
+};