title: NSScrollView: overriding scrollWheel method breaks trackpad panning
body: <p>I have a subclass of NSScrollView, like so:</p>
  
  <pre><code>class ImageScrollView : NSScrollView {
      override func scrollWheel(with event: NSEvent) {
          super.scrollWheel(with:event)
      }
  }
  </code></pre>
  
  <p>As you can see, the only thing this does is override the scrollWheel: method and call super.</p>
  
  <p>The issue I'm having is that as soon as I do this, using 2 fingers on the trackpad to try to pan around the scroll view when zoomed in stops working.  Removing the overridden method fixes it.  Any tips?</p>