title: How to get safeAreaInsets in viewWillTransitionToSize (iPhone X)
body: <p>I’m trying to update the <code>viewWillTransition(to size: with coordinator:)</code> method for iPhoneX.
  But I can’t get the destinations of the safeAreaInsets values.
  Please help!</p>
  
  <pre><code>override func viewWillTransition(to size: CGSize,
          with coordinator: UIViewControllerTransitionCoordinator) {
  
      super.viewWillTransition(to: size, with: coordinator)
  
      if #available(iOS 11.0, *) {
          if let window = UIApplication.shared.keyWindow { 
              let insets = window.safeAreaInsets
              contentFrame = CGRect(x:insets.left, y:insets.top,
                  width:size.width - insets.left - insets.right,
                  height:size.height - insets.top - insets.bottom)
          }
      } else {
          contentFrame = CGRect(x:0,y:0,width:size.width, height:size.height)
      }
      self.updateViews()
  }
  </code></pre>