Allow menus to stay open during a child view's drag and drop

ui/views/controls/menu/menu_controller.h

Index: ui/views/controls/menu/menu_controller.h
diff --git a/ui/views/controls/menu/menu_controller.h b/ui/views/controls/menu/menu_controller.h
index 30c56f0f04b88d9f36b68454c3851f526f5a1533..ff4a7dede205a27dc12b48d0b3aa9586943a8083 100644
--- a/ui/views/controls/menu/menu_controller.h
+++ b/ui/views/controls/menu/menu_controller.h
@@ -142,6 +142,15 @@ class VIEWS_EXPORT MenuController : public WidgetObserver {
   void OnDragEnteredScrollButton(SubmenuView* source, bool is_up);
   void OnDragExitedScrollButton(SubmenuView* source);
 
+  // Called by the Widget when a drag is about to start on a child view. This
+  // could be initiated by one of our MenuItemViews, or could be through another
+  // child View.
+  void OnDragWillStart();
+
+  // Called by the Widget when the drag has completed. |should_close|
+  // corresponds to whether or not the menu should close.
+  void OnDragComplete(bool should_close);
+
   // Update the submenu's selection based on the current mouse location
   void UpdateSubmenuSelection(SubmenuView* source);