title: collectionView scrolling not smooth in iOS9
body: <p>I have noticed that the scrolling of the collectionView in my app is very 'choppy' when running on iOS9.  I have taken away all items in the collectionView and left only a textView and nothing else and the scroll is still very choppy.  There are no images or heavy assets in the collectionView cells.  The scroll is smooth in iOS8.  After researching I found a few threads recommending to add the following two lines of code in the cellForItemAtIndexPath function of the collectionView just prior to returning the cell:</p>
  
  <blockquote>
    <p>cell.layer.shouldRasterize = true</p>
    
    <p>cell.layer.rasterizationScale = UIScreen.mainScreen().scale</p>
  </blockquote>
  
  <p>Adding this did not make any difference for me and the choppiness is still there.  Has anybody else experienced this and found a solution?  I have stripped down my collectionView to only containing a textView.  </p>
  
  <p>The only thing I can think of is whether the storyboard constraints are causing this behaviour.  There is nothing at all unusual about my constraints.  I have one constraint that is a less than or equals to but changing that did not help.  Thanks.</p>