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
try
		{
			startWebApp( );
			BrowserAccessor.getPreviewBrowser( false )
					.displayURL(
							createURL( report, params )
									+ "&" + new Random( ).nextInt( ) ); 
		}
		catch ( Exception e )
		{
			
		}
	}
	/**
	 * Check whether the report is a document file.
	 * 
	 * @param reportName
	 * @return true or false
	 */
	private static boolean isReportDocument( String reportName )
	{
		if ( reportName == null )
			return false;
		Pattern p = Pattern.compile( ".[a-z]{3}document$" ); 
		Matcher m = p.matcher( reportName );
		if ( m.find( ) )
			return true;
		return false;
	}
}