backup for dynamic recent tabs submenu

ui/base/models/menu_model_delegate.h

Index: ui/base/models/menu_model_delegate.h
diff --git a/ui/base/models/menu_model_delegate.h b/ui/base/models/menu_model_delegate.h
index 9e2e335faff189b2bd38d343b93d1d162d4db4da..936f87533cc741a850ad699442aa50b29eb6282b 100644
--- a/ui/base/models/menu_model_delegate.h
+++ b/ui/base/models/menu_model_delegate.h
@@ -12,6 +12,18 @@ class MenuModelDelegate {
   // Invoked when an icon has been loaded from history.
   virtual void OnIconChanged(int index) = 0;
 
+  // Invoked prior to any calls to OnItemAdded()/OnItemRemoved().
+  virtual void PrepareForChange() {}
+
+  // Invoked when adding and removing items in MenuModel, delegate should
+  // add or remove items to or from the menu as per the model.
+  virtual void OnItemAdded(int index) {}
+  virtual void OnItemRemoved(int index) {}
+
+  // Invoked when MenuModel has finisheed the changes, delegate should finalize
+  // the menu and update the UI.
+  virtual void ChangesDone() {}
+
  protected:
   virtual ~MenuModelDelegate() {}
 };