 
 package spark.components
 {
+import flash.events.Event;
 import flash.events.MouseEvent;
 import flash.geom.Point;
 

            if (!isNaN(vspDelta))
            {
                vp.verticalScrollPosition += vspDelta;
                if (vp is IInvalidating)
                    IInvalidating(vp).validateNow();
            }
        }

        event.preventDefault();
    }
    

        
        var nSteps:uint = Math.abs(delta);
        var navigationUnit:uint;
        var scrollPositionChanged:Boolean;
        
        // Scroll delta "steps".          
        navigationUnit = (delta < 0) ? NavigationUnit.DOWN : NavigationUnit.UP;
