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
+ ( maxlevels != null && maxlevels.trim( ).length( ) > 0
						? "&__maxlevels=" + maxlevels : "" ) 
				+ ( cubeMemorySize != null
						&& cubeMemorySize.trim( ).length( ) > 0
						? "&__cubememsize=" + cubeMemorySize : "" ) 
				+ "&__resourceFolder=" + encodedResourceFolder 
				+ ( asattachment != null ? asattachment : "" ) 
				+ "&__dpi=" + dpi; 
	}
	/**
	 * Start web application.
	 */
	private static void startWebApp( )
	{
		try
		{
			
			
			String debugMode = System.getProperty( REPORT_DEBUT_MODE );
			if ( debugMode == null )
			{
				
				ViewerClassPathHelper.setWorkspaceClassPath( );
			}
			WebappAccessor.start( ViewerPlugin.WEBAPP_CONTEXT );
		}
		catch ( CoreException e )
		{
			
		}