Make shelf item can be dragged when context menu is opened.

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 16ac2d4bd9c3a746d667f5c2c41e45d186e6fe61..dfbd4f3c790158cc3d7a506db4522bd79c280438 100644
--- a/ui/views/controls/menu/menu_controller.h
+++ b/ui/views/controls/menu/menu_controller.h
@@ -130,6 +130,9 @@ class VIEWS_EXPORT MenuController
 
   void set_is_combobox(bool is_combobox) { is_combobox_ = is_combobox; }
 
+  void set_cancel_active_touches(bool cancel_active_touches) {
+    cancel_active_touches_ = cancel_active_touches;
+  }
   // Various events, forwarded from the submenu.
   //
   // NOTE: the coordinates of the events are in that of the
@@ -667,6 +670,10 @@ class VIEWS_EXPORT MenuController
   // (like a context menu).
   bool is_combobox_;
 
+  // In order to make item can be dragged after context menu is opened. Cannot
+  // cancel existing touch events.
+  bool cancel_active_touches_ = true;
+
   // Set to true if the menu item was selected by touch.
   bool item_selected_by_touch_;