     }
        function write_header(header_string, url_string) {
          document.write('<h1><a href="' + window.location.pathname + '">'
                         + 'SCons Timings</a>');
          if (header_string) {
            document.write(':  ' + header_string);
          }
          if ('graph' in params) {
            document.write(':  ' + escape(params.graph))
          } else {
            document.write(':  overview');
          }
          document.write('</h1>');
        }
        if (build