Bug 194549 Memory leak in chart device renderers
After memory analysis for Chart code, it indicates java.awt.Font objects are not garbage collected. Investigating the renderer code, Graphics2D objects in IDisplayServer and IDeviceRenderer are not disposed after chart rendering finished. Need to invoke IDeviceRenderer.dispose() after ChartReportItemPresentationImpl being finished, and dispose all required resources in that method, including IDisplayServer and anything else.
chart/org.eclipse.birt.chart.device.svg/src/org/eclipse/birt/chart/device/svg/SVGRendererImpl.java
}
	protected void removeGroupStructure( Object block )
	{
		if ( ( block instanceof TitleBlock )
				|| ( block instanceof Legend )
				|| ( block instanceof Plot )
				|| ( block instanceof LabelBlock )
				|| ( block instanceof Series )
				|| ( block instanceof DataPointHints ) )
			svggc.popParent( );
	}
	protected void addGroupStructure( Object block )
	{
		if ( block instanceof TitleBlock )
		{
			Element group = svggc.dom.createElement( "g" ); 
			group.setAttribute( "id", "title" ); 
			svggc.pushParent( group );
		}
		else if ( block instanceof Legend )
		{