title: CABasicAnimation with keypath "bounds" not working
body: <p>I have the following code to animation bounds property of CALayer using CABasicAnimation. But the code doesn't seem to work.</p>
  
  <pre><code>    let fromValue = textLabel.layer.bounds
      let toValue = CGRectMake(textLabel.layer.bounds.origin.x, textLabel.layer.bounds.origin.y,   textLabel.layer.bounds.width, textLabel.layer.bounds.height + 50)
  
      let positionAnimation = CABasicAnimation(keyPath: "bounds")
      positionAnimation.fromValue = NSValue(CGRect: fromValue)
      positionAnimation.toValue = NSValue(CGRect: toValue)
      positionAnimation.duration = 1
      positionAnimation.fillMode = kCAFillModeBoth
      positionAnimation.removedOnCompletion = false
  
      textLabel.layer.addAnimation(positionAnimation, forKey: "bounds")
  </code></pre>