Bug 188283 Bubbles should be z-sorted by size in Bubble charts
Biggest bubbles should be drawn first so that there is no small bubble hidden by a bigger one.
chart/org.eclipse.birt.chart.engine/src/org/eclipse/birt/chart/event/MarkerInstruction.java
{
		return iInstruction;
	}
	/**
	 * Returns the size of marker
	 * 
	 * @return marker size
	 */
	public final double getMarkerSize( )
	{
		return iMarkerSize;
	}
	/**
	 * @return Returns the minimum bounds required to contain the rendering area
	 *         of associated rendering event.
	 */
	public final Bounds getBounds( )
	{
		try
		{
			return pre.getBounds( );
		}
		catch ( Exception ex )
		{
			ex.printStackTrace( );
		}
		return null;
	}
}