title: UILabel numberOfLines change with animation
body: <p>I have a <code>UILabel</code> inside a <code>UIStackView</code>, and the stack view is inside another <code>UIScrollView</code>, I'm using auto layout. The label has single line (ie. <code>numberOfLines</code> equal to 1) and in a few cases I need to set it to multiline (ie. <code>numberOfLines</code> equal to 0) with an animation that expands it.</p>
  
  <pre><code>func expand() {
      label.numberOfLines = 0
  }
  </code></pre>
  
  <p>when I click expand:</p>
  
  <pre><code>messageView.expand()
  UIView.animate(withDuration: 0.3) {
      self.layoutIfNeeded()
  }
  </code></pre>
  
  <p>However, when it expands, the label's frame isn't updated and I have to scroll (the scroll view) to make it fully visible. What could be wrong?</p>
  
  <p>Thanks!</p>