title: For Exoplayer, can I add (or enable?) a button to toggle Closed Captions using the standard controls, e.g. in PlayerControlView?
body: <p>My app is playing video streams with Exoplayer.</p>
  
  <p>I am using the default controls by using "PlayerControlView".</p>
  
  <p>I need to add a toggle button to show/hide closed captions ( subtitles ). </p>
  
  <p>Is there a simple way to add such a button to the standard controls?</p>
  
  <p>( Note: I am aware that it's possible to completely customize the controls by creating custom views and firing events on Exoplayer, that's not what I'm asking here. )</p>
  
  <p>Put in a different way: What's the easiest way to have a toggle button for toggling the visibility of closed captions ?</p>