title: Notification when movie player control gets visible/hidden?
body: <p>I just want to know if its possible to get a notification when the playback control gets visible or hidden?</p>
  
  <p>For example, I want to present a video with the style:</p>
  
  <pre><code>self.moviePlayerController.controlStyle = MPMovieControlStyleEmbedded;
  </code></pre>
  
  <p>When the video starts playing, the playback controls gets visible and automatically disappears. If the user just tab on the video, the controls appear.</p>
  
  <p>I need a notification so i can adjust my view (reposition some additional buttons under the <code>MPMoviePlayerController</code> view. 
  Is that possible? Because unfortunately I found nothing in the documentation.</p>