title: UIPopoverPresentationController has wrong anchor position on iPhone 6 plus and 7 plus when it's in landscape mode
body: <p>I present a popover programmatically from a button on toolbar. I successfully implemented it on Xcode 8.1. </p>
  
  <pre><code>            _myMapViewController.modalPresentationStyle = UIModalPresentationPopover;
  
              switch ([[UIApplication sharedApplication] statusBarOrientation]) {
                  case UIInterfaceOrientationPortrait:
                  case UIInterfaceOrientationPortraitUpsideDown:
                      // Resize Popover
                      _myMapViewController.preferredContentSize = self.popoverSizeForPortrait;
                      break;
                  case UIInterfaceOrientationLandscapeLeft:
                  case UIInterfaceOrientationLandscapeRight:
                      // Resize Popover
                      _myMapViewController.preferredContentSize = self.popoverSizeForLandscape;
                      break;
                  default:
                      //do nothing
                      break;
              }
  
              UIPopoverPresentationController *popoverPresentation = _myMapViewController.popoverPresentationController;
              [popoverPresentation setBarButtonItem:_mapButton];
              [popoverPresentation setPermittedArrowDirections:UIPopoverArrowDirectionDown];
              [popoverPresentation setDelegate:self];
  
              [self presentViewController:_myMapViewController animated:YES completion:nil];
  </code></pre>
  
  <p>Below is a successful outcome on iPhone 7. You see a popover of a map anchored to compass button on the bottom left.
  <a href="https://i.stack.imgur.com/v0Tts.png" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/v0Tts.png" alt="iPhone 7 simulator in landscape"></a></p>
  
  <p>However, when I run the same code with iPhone 6 Plus and 7 Plus simulators, the popover in landscape mode is shown from unknown (and unintended) anchor) like this:
  <a href="https://i.stack.imgur.com/0mtso.png" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/0mtso.png" alt="enter image description here"></a></p>
  
  <p>Showing the popover in portrait mode has no issues. Any idea for resolution would be appreciated. </p>