 import mx.events.FlexEvent;
 import mx.events.PropertyChangeEvent;
 import mx.events.PropertyChangeEventKind;
+import mx.utils.MatrixUtil;
+
+import spark.components.ResizeMode;
+import spark.core.IViewport;
+import spark.core.MaskType;
 import spark.events.RendererExistenceEvent;
-import spark.core.MaskType;
 import spark.layouts.BasicLayout;
 import spark.layouts.supportClasses.LayoutBase;
-import mx.utils.MatrixUtil;
 
 use namespace mx_internal;
 

        if (_layout)
        {
            _layout.target = null;
            _layout.removeEventListener("propertyChange", redispatchLayoutEvent);
        }
        _layout = value; 
        if (_layout)
        {
            _layout.target = this;
            _layout.addEventListener("propertyChange", redispatchLayoutEvent);
        }

        invalidateSize();

    [Inspectable(category="General")]    

    /**
     *  @copy spark.core.IViewport#contentHeight
     *  
     *  @langversion 3.0
     *  @playerversion Flash 10
