[spark_skins] Halo CheckBox with custom skin has two checkbox icons (and looks pretty messed up, yo)

found in trunk 4.0.0.8974.

Steps to reproduce:
1. Compile and run attached .MXML file:

<?xml version="1.0" encoding="utf-8"?>
<s:Application xmlns:fx="http://ns.adobe.com/mxml/2009"
xmlns:s="library://ns.adobe.com/flex/spark"
xmlns:mx="library://ns.adobe.com/flex/halo">

<mx:CheckBox id="cb"
label="Halo CheckBox "
skin="mx.skins.spark.CheckBoxSkin"
height="60"
labelPlacement="left"
initialize="cb.label += '(' + mx_internal::VERSION + ')';"/>

</s:Application>

Actual Results:
TWO checkbox boxes?

Expected Results:
One checkbox box.

Workaround (if any):
Dont set the "skin" style. Set the "icon" style instead.