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..77cad7e207b2c38a1dc8a359cea7a6e13ac755d2 100644
--- a/ui/views/controls/menu/menu_controller.h
+++ b/ui/views/controls/menu/menu_controller.h
@@ -92,6 +92,14 @@ class VIEWS_EXPORT MenuController : public WidgetObserver {
   // Whether or not drag operation is in progress.
   bool drag_in_progress() const { return drag_in_progress_; }
 
+  // Since general Views and MenuItemViews have different mechanisms for
+  // implementing drag, it is possible that a child view will want to use
+  // its own dragging, in which case it needs to notify the controller that
+  // a drag is in progress to avoid closing the active menu.
+  void set_drag_in_progress(bool drag_in_progress) {
+    drag_in_progress_ = drag_in_progress;
+  }
+
   // Returns the owner of child windows.
   // WARNING: this may be NULL.
   Widget* owner() { return owner_; }