[Mac] App Menu Animated Icon

chrome/browser/ui/cocoa/menu_button.h

 // Copyright (c) 2011 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #ifndef CHROME_BROWSER_UI_COCOA_MENU_BUTTON_H_
 #define CHROME_BROWSER_UI_COCOA_MENU_BUTTON_H_
 
 #import <Cocoa/Cocoa.h>
 
 #include "base/mac/scoped_nsobject.h"
@@ skipping 31 matching lines @@
 // menu will only be opened when clicked and held.
 @property(assign, nonatomic) BOOL openMenuOnClick;
 
 // Whether or not to open the menu when the right button is clicked.
 @property(assign, nonatomic) BOOL openMenuOnRightClick;
 
 // Returns the rectangle that menus are anchored at. Can be overridden by
 // subclasses, returns -bounds by default.
 - (NSRect)menuRect;
 
+// Called when the menu is about to be shown. Implemented by subclasses.
+- (void)willShowMenu;
+
 @end  // @interface MenuButton
 
 // Available for subclasses.
 @interface MenuButton (Protected)
 - (void)configureCell;
 @end
 
 #endif  // CHROME_BROWSER_UI_COCOA_MENU_BUTTON_H_