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

ui/views/controls/menu/menu_delegate.h

Index: ui/views/controls/menu/menu_delegate.h
diff --git a/ui/views/controls/menu/menu_delegate.h b/ui/views/controls/menu/menu_delegate.h
index 7f4b74fb53c4b679c0d2372f222b1349d48c8fde..6c51d5948b476685f17c7541ed2e1feab6c57517 100644
--- a/ui/views/controls/menu/menu_delegate.h
+++ b/ui/views/controls/menu/menu_delegate.h
@@ -208,6 +208,11 @@ class VIEWS_EXPORT MenuDelegate {
   virtual void DropMenuClosed(MenuItemView* menu) {
   }
 
+  // Returns true if the menu should close upon a drag completing. Defaults to
+  // true. This is only invoked for drag and drop operations performed on child
+  // Views that are not MenuItemViews.
+  virtual bool ShouldCloseOnDragComplete();
+
   // Notification that the user has highlighted the specified item.
   virtual void SelectionChanged(MenuItemView* menu) {
   }