                     vsbVisible = (contentH >= (viewportH + SDT));
                 }                        
                 break;
-
+            
+            case ScrollPolicy.OVERLAY:
+                vsbVisible = scroller.verticalScrollInProgress;
+                vsbTakeUpSpace = false;
+                break;
+            
             default:
                 vsbVisible = false;
         }

        // then prefer to show the "non-dependent" auto scrollbar if we added the second
        // "dependent" auto scrollbar because of the space consumed by the first.
        
        if (hsbVisible && vsbVisible) 
        {
            if (hsbFits(w, h) && vsbFits(w, h))
            {

        // the viewport's size was explicitly set, then we just use that. 
        
        if (isNaN(explicitViewportW))
            viewportW = w - ((vsbVisible && vsbTakeUpSpace) ? (minViewportInset + vsbRequiredWidth()) : (minViewportInset * 2));
        else 
            viewportW = explicitViewportW;
        
        if (isNaN(explicitViewportH))
            viewportH = h - ((hsbVisible && hsbTakeUpSpace) ? (minViewportInset + hsbRequiredHeight()) : (minViewportInset * 2));
        else 
            viewportH = explicitViewportH;

