[spark_skins] Button does not resize to fit icon

Steps to reproduce:
1. Compile & run:
<?xml version="1.0" encoding="utf-8"?>
<FxApplication xmlns="http://ns.adobe.com/mxml/2009" >
<layout>
<VerticalLayout/>
</layout>
<Script>
<![CDATA[
[Bindable]
[Embed(source="disabledIcon.gif")]
public var digif:Class;

]]
>
</Script>

<Button id="btn" icon="

" />
<Label text="

"/>
</FxApplication>

Actual Results:
Button height is 31 width 70 - icon does not fit inside Button

Expected Results:
Before Spark skins, button height would report back as 35 and width 70 and icon would fit inside Button.

Workaround (if any):