Button subclass with Alpha
<p>I'm trying to set the transparency of a button using the API level 10 (so no view.setAlpha).
I wrapped the <code>Button.onDraw</code> calling a <code>Canvas.saveLayerAlpha</code> on a subclass: this works with the text but not with the button background.</p>

<p>I want to make it possible to leave the current button's background management, should I draw the button background myself without calling <code>super.onDraw</code>? How to get a consistent reference to the current button background inside the <code>onDraw</code> extent?</p>
