Get the map overlay marker icon during onTap
<p>I'm using an ItemizedOverlay containing a list of OverlayItems to display markers on top of a MapView.  My problem is that when an OverlayItem uses the default marker defined for the overlay, its getMarker() method returns null.  Is there another way I can get that marker image?  I'd like to see if I can animate it during onTap().</p>

<p>I'm showing a bunch of markers on the map, many of which use the same image, so I thought it best to make use of the overlay's default image to save memory.  For this app it's possible there could be more than 100 markers displayed for a given overlay.</p>
