title: Is KVO on AVPlayerItem.loadedTimeRanges possible?
body: <p>Apples documentation alludes to it, but how do you set up key-value observation for the loadedTimeRanges property of AVPlayerItem? That property is an NSArray that doesn't change, so you can't just use <code>playerItem addObserver:self forKeyPath:@"loadedTimeRanges ...</code></p>
  
  <p>Or is there another way to get notifications or updates whenever this changes?</p>