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.engine/src/org/eclipse/birt/chart/device/IDisplayServer.java
*            being requested
	 * 
	 * @return A device specific font
	 */
	Object createFont( FontDefinition fd );
	/**
	 * Attempts to create a new color resource associated with a specific device
	 * 
	 * @param cd
	 *            A color description for which a device specific resource is
	 *            being requested
	 * 
	 * @return A device specific color
	 */
	Object getColor( ColorDefinition cd );
	/**
	 * Returns the resolution of the device in dots per inch As an example, for
	 * a display screen, the dots correspond to pixels and a typical value for a
	 * Win32 OS is 96 DPI.
	 * 
	 * @return The integral dots per inch associated with the device
	 */
	int getDpiResolution( );
	/**
	 * Sets the dpi resolution. This defines how many dots per inch to use for
	 * rendering the chart. This is optional, the display server will compute
	 * the default dpi resolution of the display where the chart is rendered. It
	 * is mostly intended to be used for creating high resolution images.
	 * 
	 * @param dpi