docs: function loadSource(url) {
          if (!TraceKit.remoteFetching) { //Only attempt request if remoteFetching is on.
              return '';
          }
          try {
              var getXHR = function() {
                  try {
                      return new window.XMLHttpRequest();
                  } catch (e) {
                      // explicitly bubble up the exception if not found
                      return new window.ActiveXObject('Microsoft.XMLHTTP');
                  }
              };
  
              var request = getXHR();
              request.open('GET', url, false);
              request.send('');
              return request.responseText;
          } catch (e) {
              return '';
          }
      }