Missing code in Chromecast sample about castvideos-chrome

[rafa8626]

I tried the following when I was reading the documentation:

var session = cast.framework.CastContext.getInstance().getCurrentSession();
var media = session.getMediaSession();
media.editTracksInfo(tracks, function() {}, function(e) { console.error(e); });

And when it does that it returns the following error:
Object {code: "session_error", description: "INVALID_PARAMS", details: {reason: "INVALID_PARAMS", type: "INVALID_REQUEST"} }

Am I missing something? Or am I instantiating the Media element wrong?

If I need to call a new Media object, from the CastVideos.js file, how can I access the sessionId and the mediaSessionId that I need for this?