[flexcoders] How to embed icons in MenuBar?

[nathanleewei]

[Embed(source="/assets/document.png")]
private static const document_icon:Class;


<mx:MenuBar id="menuBar" width="100%" labelField="@label" 
iconField="@icon" styleName="menuBar" itemClick="onMenuBar(event)">
                <mx:XMLList>
                    <menuitem label="File">
                        <menuitem label="New" icon="document_icon" />

it has no effect?!