title: Xcode 8.1 : No options for update frames on changing constraints
body: <p>I've done the following steps:</p>
  
  <ol>
  <li>Added scrollview to main view.</li>
  <li><p>Added constraints 0,0,0,0 top, left,bottom, right to scrollview.
  RESULT: Scrollview updates frames</p></li>
  <li><p>Added button to scrollview</p></li>
  <li>and added constraints 0,0,0,0 top, left,bottom,right and even width,height</li>
  </ol>
  
  <p>RESULT : Can't update frame of UIButton </p>
  
  <p>I don't why I can't update frame after applying constraint to button view .</p>
  
  <p>error says: has ambiguous scrollable height
  <a href="https://i.stack.imgur.com/aLd5y.png" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/aLd5y.png" alt="enter image description here"></a></p>
  
  <p>if I add other views or change anything like give height constraint to scrollview , it becomes red with the same error.</p>
  
  <p>Any suggestion.</p>