title: Why isn't my UIGraphicsImageRenderer drawing (iOS 10)?
body: <p>UIGraphicsImageRenderer is the new iOS 10 way to create an image context and draw into it. I'm trying to use UIGraphicsImageRenderer to draw a simple image:</p>
  
  <pre><code>let size = CGSize(width:100,height:100)
  let f = UIGraphicsImageRendererFormat()
  f.opaque = false
  let r = UIGraphicsImageRenderer(size:size, format: f)
  let im = r.image { _ in
      let p = UIBezierPath(ovalIn: CGRect(origin: CGPoint.zero, size: size))
      UIColor.blue().setFill()
      p.fill()
  }
  let iv = UIImageView(image:im)
  iv.frame.origin = CGPoint(x: 200, y: 200)
  self.view.addSubview(iv)
  </code></pre>
  
  <p>I expect to see a blue filled circle. But I don't see anything. What am I doing wrong?</p>
  
  <p>PS I'm using Xcode 8 Seed 3, if it matters.</p>