Bug 209119 Need WebViewer provide cancel function
Need WebViewer provide a cancel function, this will be used to cancel current report execution during designer preview.
viewer/org.eclipse.birt.report.viewer/src/org/eclipse/birt/report/viewer/utilities/WebViewer.java
{
		startWebApp( );
	}
	/**
	 * Stop the web server
	 */
	public static void stop( )
	{
		stopWebApp( );
	}
	/**
	 * Displays the specified url.
	 * 
	 * @param report
	 *            report report
	 * @param format
	 *            report format
	 */
	public static void display( String report, String format )
	{
		display( report, format, true );
	}
	/**
	 * Displays the specified url.
	 * 
	 * @param report
	 * @param format
	 * @param allowPage
	 */
	public static void display( String report, String format, boolean allowPage )