title: Get the CGRect frame of the inner contentView of a UINavigationController during or before loadView
body: <p>Apple's docs say:</p>
  
  <pre><code>Note: Because the amount of space available for the custom view can vary
  (depending on the size of the other navigation views), your custom view’s
  autoresizingMask property should be set to have a flexible width and height.
  Before displaying your view, the navigation controller automatically
  positions and sizes it to fit the available space.
  </code></pre>
  
  <p>That's great, except ... I need to know the size UINavController will use <em>BEFORE</em> the view is added to the frame, because the content I'll be displaying is different depending on the size.</p>
  
  <p>This is inside the "loadView" method of a UIViewController that's being added to the UINavigationController.</p>