selectTextLanguage while not displaying text doesn't update active track

[anuragkalia]

Have you read the FAQ and checked for duplicate open issues?

Yes
What version of Shaka Player are you using?
Latest

Can you reproduce the issue with our latest release version?
Yes

Can you reproduce the issue with the latest code from master?
Yes.

Are you using the demo app or your own custom app?
Demo app.

What browser and OS are you using?
Chrome, Mac

What did you do?

1. Open https://shaka-player-demo.appspot.com/demo/#audiolang=en-GB;textlang=en-GB;uilang=en-GB;asset=https://storage.googleapis.com/shaka-demo-assets/angel-one/dash.mpd;panel=SEARCH;build=uncompiled
2. Run shakaDemoMain.player_.selectTextLanguage('el') in console.
3. Run shakaDemoMain.player_.getTextTracks() in console.

What did you expect to happen?
I expected ‘el’ to be the active text track.

What actually happened?
But ‘en’ is the active text track instead of ‘el’. This is happening because in chooseStreamsAndSwitch_, we do not switch the text stream if it is not visible. That logic is also responsible for updating the active text stream.