title: UISlider in UIBarButtonItem impacts animation behavior
body: <p>In IB, I set a view MyView with an UIToolBar and I drop an UISlider on it. IB automatically embeds it in an UIBarButtonItem and sets its view with the UISlider.</p>
  
  <p>I display this MyView in a navigation controller with animation.</p>
  
  <p><code>UIViewController *myVC = [[UIViewController alloc] initWithNibName:@"MyView" bundle:nil];<br>
  [self.navigationController pushViewController:myVC animated:YES];<br>
  [myVC release];</code></p>
  
  <p>MyView is displayed but without animation. Apart from that, everything works fine, I can use the UISlider as needed.
  If I remove the UISlider from the toolbar or if I put the UISlider in the view itself, not in the toolbar, MyView is displayed with animation.
  I have tried the same with an UIProgressView instead and it worked fine ( view is displayed with animation ). It seems that UISlider as customView of an UIBarButtonItem prevents the animation.
  I have also checked for any possible leaking.</p>
  
  <p>Any idea ?
  Thanks
  Tart.</p>