Bug 851641. Ignore move/resize notifications for popups whose widget is hidden because this likely means they are notifications about our own move/resize requests. r=mats

layout/xul/base/src/nsXULPopupManager.cpp

@@ -341,6 +341,10 @@ nsMenuPopupFrame* GetPopupToMoveOrResize(nsIFrame* aFrame)
   if (menuPopupFrame->PopupState() != ePopupOpenAndVisible)
     return nullptr;
 
+  nsIWidget* widget = menuPopupFrame->GetWidget();
+  if (widget && !widget->IsVisible())
+    return nullptr;
+
   return menuPopupFrame;
 }