Class selectors which specify padding styles do not work in VGroup, HGroup.

Steps to reproduce:
1. Look at the ASDoc for VGroup, and confirm that paddingLeft, paddingRight, etc... are supported styles.
2. Define a class selector:
<fx:Style>
@namespace s "library://ns.adobe.com/flex/spark";

.paddedBox

{ paddingLeft: 20; paddingRight: 20; paddingTop: 20; paddingBottom: 20; color: #00ff00; }

</fx:Style>

2. Use it:
<s:VGroup id="container" styleName="paddedBox">
<s:Label text="

{multiLineText}

"/>
</s:VGroup>

Actual Results:
No padding occurs.

Expected Results:
Padding should occur.

Workaround (if any):
<s:VGroup id="container" paddingLeft="20" paddingRight="20" paddingTop="20" paddingBottom="20">