Add the button style for combobox

ui/views/controls/menu/menu_runner.h

Index: ui/views/controls/menu/menu_runner.h
diff --git a/ui/views/controls/menu/menu_runner.h b/ui/views/controls/menu/menu_runner.h
index 277ffd5334a41005ec75d84762cc579fadb4c6d5..6b46362f18e76431451d4a786190e05a6b69be7a 100644
--- a/ui/views/controls/menu/menu_runner.h
+++ b/ui/views/controls/menu/menu_runner.h
@@ -18,6 +18,7 @@ namespace views {
 
 class MenuButton;
 class MenuModelAdapter;
+class MenuRunnerHandler;
 class Widget;
 
 namespace internal {
@@ -25,6 +26,10 @@ class DisplayChangeListener;
 class MenuRunnerImpl;
 }
 
+namespace test {
+class MenuRunnerTestAPI;
+}
+
 // MenuRunner is responsible for showing (running) the menu and additionally
 // owning the MenuItemView. RunMenuAt() runs a nested message loop. It is safe
 // to delete MenuRunner at any point, but MenuRunner internally only deletes the
@@ -112,10 +117,19 @@ class VIEWS_EXPORT MenuRunner {
   base::TimeDelta closing_event_time() const;
 
  private:
+  friend class test::MenuRunnerTestAPI;
+
+  // Sets an implementation of RunMenuAt. This is intended to be used at test.
+  void SetRunnerHandler(scoped_ptr<MenuRunnerHandler> runner_handler);
+
   scoped_ptr<MenuModelAdapter> menu_model_adapter_;
 
   internal::MenuRunnerImpl* holder_;
 
+  // An implementation of RunMenuAt. This is usually NULL and ignored. If this
+  // is not NULL, this implementation will be used.
+  scoped_ptr<MenuRunnerHandler> runner_handler_;
+
   scoped_ptr<internal::DisplayChangeListener> display_change_listener_;
 
   DISALLOW_COPY_AND_ASSIGN(MenuRunner);