code: function() {
          var xdr;
  
          if (Ext.ieVersion >= 8) {
              xdr = new XDomainRequest();
          } else {
              Ext.Error.raise({
                  msg: 'Your browser does not support CORS'
              });
          }
  
          return xdr;
      }
docs: Creates the appropriate XDR transport for this browser.
  - IE 7 and below don't support CORS
  - IE 8 and 9 support CORS with native XDomainRequest object
  - IE 10 (and above?) supports CORS with native XMLHttpRequest object
  @private