title: Android onSystemUiVisibilityChange is never called
body: <p>Using the code verbatim from <a href="https://developer.android.com/training/system-ui/visibility.html" rel="nofollow">https://developer.android.com/training/system-ui/visibility.html</a> in an app on a Google Nexus 4 (OS 4.4), and the onSystemUiVisibilityChange callback is never invoked. I might be seriously not understanding the conditions when this is to be invoked. I open up another app on the device that is in full screen mode and the status bar is hidden. Callback not invoked. Is this only meant for use with my own app? </p>
  
  <p>What I'm really trying to do is detect if the status bar is displayed so I'll know I can post a notification with a ticker text that I know a user will see. If they're in a full screen app, they won't see my ticker text and that would not be ideal for me.</p>