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/PrimitiveRenderEvent.java
* @return Returns the depth of current event.
	 */
	public final double getDepth( )
	{
		return dDepth;
	}
	
	
	/**
	 * @return A reference to the LineAttributes
	 */
	public LineAttributes getLineAttributes( )
	{
		return null;
	}
	
	/**
	 * @return A reference to the Background Fill
	 */
	public Fill getBackground( )
	{
		return null;
	}
	
	public Label getLabel( )
	{
		return null;
	}
	
}