Setting a custom icon on the MX Button control in Flex

<?xml version="1.0" encoding="utf-8"?>
<!-- http://blog.flexexamples.com/2010/11/08/setting-a-custom-icon-on-the-mx-button-control-in-flex/ -->
<mx:Application name="MX_Button_upIcon_test"
        xmlns:mx="http://www.adobe.com/2006/mxml"
        layout="vertical"
        verticalAlign="middle"
        backgroundColor="white">
 
    <mx:Style>
        .titleWindowIconAsIcon {
            upIcon: Embed("Assets.swf#CloseButtonUp");
            overIcon: Embed("Assets.swf#CloseButtonOver");
            downIcon: Embed("Assets.swf#CloseButtonDown");
            disabledIcon: Embed("Assets.swf#CloseButtonDisabled");
        }
 
        .titleWindowIconAsSkin {
            upSkin: Embed("Assets.swf#CloseButtonUp");
            overSkin: Embed("Assets.swf#CloseButtonOver");
            downSkin: Embed("Assets.swf#CloseButtonDown");
            disabledSkin: Embed("Assets.swf#CloseButtonDisabled");
        }
    </mx:Style>
 
    <mx:Button styleName="titleWindowIconAsIcon" label="Button" />
    <mx:Button styleName="titleWindowIconAsSkin" />
 
</mx:Application>