 import mx.events.CollectionEvent;
 import mx.events.CollectionEventKind;
 import mx.events.PropertyChangeEvent;
+import mx.utils.MatrixUtil;
 
 import spark.components.supportClasses.GroupBase;
 import spark.events.RendererExistenceEvent;

    
    /**
     *  @private
     *  Called before super.updateDisplayList() if layout.useVirtualLayout=true.
     *  Copies virtualRendererIndices to oldRendererIndices, clears virtualRendererIndices
     *  (which will be repopulated by subsequence getVirtualElementAt() calls), and

import flash.display.DisplayObject;
import flash.events.Event;
import flash.events.IEventDispatcher;
import flash.geom.PerspectiveProjection;
import flash.geom.Rectangle;

import mx.collections.IList;
import mx.core.IDataRenderer;
