      * 
      *  Updated by createGridElement().
      */
-    private const elementToFactoryMap:Dictionary = new Dictionary();    
+    private const elementToFactoryMap:Dictionary = new Dictionary();
+    
+    /**
+     *  @private
+     *  Used by scrollPositionChanged() to determine which scroll position properties changed.
+     */    
+    private var oldVerticalScrollPosition:Number = 0;
+    private var oldHorizontalScrollPosition:Number = 0;
     
     //--------------------------------------------------------------------------
     //

    /**
     *  @private
     *  The previous values of the corresponding variables.   Set by layoutItemRenderers()
     *  and only valid during updateDisplayList().
     */
    private var oldVisibleRowIndices:Vector.<int> = new Vector.<int>(0);
    private var oldVisibleColumnIndices:Vector.<int> = new Vector.<int>(0);


import mx.collections.IList;
import mx.core.ClassFactory;
import mx.core.IContainerInvalidating;
import mx.core.IFactory;
import mx.core.IInvalidating;
import mx.core.IUITextField;
import mx.core.IVisualElement;
