The bandwidth of the chosen track (null when 'type' is 'text').
The presentation's max segment duration in seconds, or NaN.
This is currently only supported while using Shaka.
'true' if this track choice was made by the player's ABR algorithm for
adaptation; 'false' if the choice was made by the application.
The timestamp the state was entered, in seconds since 1970 (i.e.
Date.now() / 1000).
The type of track chosen ('variant' or 'text'). A 'variant' describes a
combination of an audio and video stream which could be played together.
It's possible to have a video/audio only variant.