code>mask</code>
object. To ensure that masking works when the Stage is scaled, the
<code>mask</code> display object must be in an active part of the display
list. The <code>mask</code> object itself is not drawn. Set
<code>mask</code> to <code>null</code> to remove the mask.</p>
<p>To be able to scale a mask object, it must be on the display list. To
be able to drag a mask Sprite object(by calling its
<code>startDrag()</code> method), it must be on the display list. To call
the <code>startDrag()</code> met