title: Popovercontroller is automatically resizing
body: <p>in my App i have a Longpress Gesture on my TableCell. On Lonpress a Popover opens. The Popover inerhits a NavigationController.
  Here is the code:</p>
  
  <pre><code>var navigationController = new UINavigationController();
  
  //Page 1 
  var contPage1 = new UIViewController();
  this._movePicker = new UIDatePicker();
  var btnPage1 = new UIButton();
  btnPage1.Frame = new RectangleF(0,260, 300,40);
  contPage1.View.AddSubview(this._movePicker);
  contPage1.View.AddSubview(btnPage1);
  
  //Page 2
  var contPage2 = new UIViewController();
  var btnPage2 = new UIButton();
  var textField = new UITextField();
  textField.Frame = new RectangleF(0,35,300,150);
  btnPage2.Frame = new RectangleF(0,260,300,40);
  contPage2.View.AddSubview(btnPage2);
  contPage2.View.AddSubview(textField);
  
  // startPopover
  this.PopoverController = new UIPopoverController(navigationController);
  this.PopoverController.PopoverContentSize = new SizeF(300,340);
  //Navigate on the first site
  navigationController.PushViewController(contPage1, true);
  btnPage1.TouchUpInside(s,e) =&gt; navigationController.PushViewController(contPage2, true);
  
  this.PopoverController.PresentFromRect(locationinView, btn, UIPopoverDirection.Any, true);
  </code></pre>
  
  <p>Okay. This works fine. A popover appears. on the FirstView i click on the button and it navigates me to the second page. After that the keyboard appears and i can write something in the textField. If i close the keyboard the popover changes his size. It now takes the entire height of the iPad´s display.</p>
  
  <p>But why does it resize. I set the size of the Popover to 300, 400</p>