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

Source/core/html/track/TrackEvent.cpp

Index: Source/core/html/track/TrackEvent.cpp
diff --git a/Source/core/html/track/TrackEvent.cpp b/Source/core/html/track/TrackEvent.cpp
index 05efafd93932c560fbe947ea1a426318bc47628d..293a9478f924966479334890e35c1cf180cf2ff9 100644
--- a/Source/core/html/track/TrackEvent.cpp
+++ b/Source/core/html/track/TrackEvent.cpp
@@ -24,9 +24,13 @@
  */
 
 #include "config.h"
-
 #include "core/html/track/TrackEvent.h"
 
+#include "bindings/core/v8/UnionTypesCore.h"
+#include "core/html/track/AudioTrack.h"
+#include "core/html/track/TextTrack.h"
+#include "core/html/track/VideoTrack.h"
+
 namespace blink {
 
 TrackEventInit::TrackEventInit()
@@ -53,6 +57,26 @@ const AtomicString& TrackEvent::interfaceName() const
     return EventNames::TrackEvent;
 }
 
+void TrackEvent::track(VideoTrackOrAudioTrackOrTextTrack& returnValue)
+{
+    if (!m_track)
+        return;
+
+    switch (m_track->type()) {
+    case TrackBase::TextTrack:
+        returnValue.setTextTrack(toTextTrack(m_track.get()));
+        break;
+    case TrackBase::AudioTrack:
+        returnValue.setAudioTrack(toAudioTrack(m_track.get()));
+        break;
+    case TrackBase::VideoTrack:
+        returnValue.setVideoTrack(toVideoTrack(m_track.get()));
+        break;
+    default:
+        ASSERT_NOT_REACHED();
+    }
+}
+
 void TrackEvent::trace(Visitor* visitor)
 {
     visitor->trace(m_track);