Flex中如何通过horizontalGap样式，设置TabBar控件各个Tab间空格间距

<?xml version="1.0" encoding="utf-8"?>
<mx:Application xmlns:mx="http://www.adobe.com/2006/mxml"
layout="vertical"
verticalAlign="middle"
backgroundColor="white">

<mx:Array id="arr">
<mx:Object label="The quick" />
<mx:Object label="brown fox" />
<mx:Object label="jumped over" />
<mx:Object label="the lazy fox" />
</mx:Array>

<mx:ApplicationControlBar dock="true">
<mx:Form>
<mx:FormItem label="horizontalGap:">
<mx:HSlider id="slider"
minimum="-5"
maximum="10"
value="-1"
liveDragging="true"
snapInterval="1"
tickInterval="1" />
</mx:FormItem>
</mx:Form>
</mx:ApplicationControlBar>

<mx:TabBar id="tabBar"
horizontalGap="{slider.value}"
dataProvider="{arr}" />

</mx:Application>