Ensure that a TrackList won't be collected if it has custom properties.

** Add a custom property to a track.
EXPECTED (video.textTracks.length == '1') OK
RUN(video.textTracks.myProperty = 'chicken salad!')
EXPECTED (video.textTracks.length == '1') OK
EXPECTED (video.textTracks.myProperty == 'chicken salad!') OK

** Force garbage collection.
EXPECTED (video.textTracks.length == '1') OK
EXPECTED (video.textTracks.myProperty == 'chicken salad!') OK

END OF TEST

