Subtitles doesn't work on Chromecast using 7.9.0.
On 7.9.0, casting a video with subtitles turned on will only cast the video itself, not the subtitles. On 7.8.7 and a few versions before, casting a video with subtitles do work, it's just that it's not styled (Black border, generic font).
Also. "jwplayer.cast.availability" is not available in 7.9.0. I kinda needed that to hide some contents while casting is not available.