transform.pixelBounds は addChild されてから

/**
 * Copyright bkzen ( http://wonderfl.net/user/bkzen )
 * MIT License ( http://www.opensource.org/licenses/mit-license.php )
 * Downloaded from: http://wonderfl.net/c/csIa
 */

package {
    import flash.display.Sprite;
    import com.actionscriptbible.Example;
    import flash.display.Graphics;
    public class FlashTest extends Example {
        public function FlashTest() {
            // write as3 code here..
            var sp:Sprite = new Sprite();
            trace(sp.transform.pixelBounds);
            var g:Graphics = sp.graphics;
            g.beginFill(0x0099CC);
            g.drawCircle(20, 30, 50);
            trace(sp.transform.pixelBounds);
            addChildAt(sp, 0);
            trace(sp.transform.pixelBounds);
        }
    }
}