Prefer a new cue list in simple_text_displayer.
Prefer a new cue list in simple_text_displayer.

On some platforms, the cue list object returned by TextTrack
might not update as cues are added and removed.
To account for that, this changes simple_text_displayer to fetch
a new cue list when one is available.

Change-Id: I9eda19197b343b0f6385a8cbb64cef8f2b31b9b9

tvoli/shaka-player,shaka-project/shaka-player,shaka-project/shaka-player,tvoli/shaka-player,tvoli/shaka-player,shaka-project/shaka-player,tvoli/shaka-player,shaka-project/shaka-player