title: Subviews added to documentView of NSScrollView not showing up
body: <p>I have a <code>NSView</code> wrapped in a <code>NSScrollView</code> using the IB. In the initialization function of the view (class is <code>NoteView</code>) containing the <code>NSScrollView</code>, I attempt to add subviews to the <code>NSView</code> as follows:</p>
  
  <pre><code>// Initialize custom view with width 802 and height 130, call it initialSubview
  // Set initialSubview's frame origin to (20.0, 580.0). documentView of scrollView
  // is size (842.0, 740.0)
  // Let innerView be the documentView of the scrollView (I have an IBOutlet attaching
  // the scrollView's document view to innerView)
  
  [innerView addSubview:initialSubview];
  </code></pre>
  
  <p>When I do this, nothing shows up. Likewise, trying this:</p>
  
  <pre><code>[[[scrollView] documentView] addSubview:initialSubview];
  </code></pre>
  
  <p>doesn't work either. However, if I added it to the contentView:</p>
  
  <pre><code>[[[scrollView] contentView] addSubview:initialSubview];
  </code></pre>
  
  <p>The subview shows up fine. Any ideas?
  As an addendum, if I add something like an <code>NSButton</code> to the documentView in the IB, nothing
  shows up as well.</p>