adding isFlipped to userpane

git-svn-id: https://svn.wxwidgets.org/svn/wx/wxWidgets/trunk@73265 c3d73ce0-8a6f-49c7-b76d-6d57e0e08775

src/osx/cocoa/window.mm

@@ -783,6 +783,14 @@ void wxWidgetCocoaImpl::SetupMouseEvent( wxMouseEvent &wxevent , NSEvent * nsEve
     }
     [super removeTrackingRect:tag];
 }
+
+#if wxOSX_USE_NATIVE_FLIPPED
+- (BOOL)isFlipped
+{
+    return YES;
+}
+#endif
+
 @end // wxNSView
 
 //