code: function addExtraHeaders(request, headers) {
          for (var name in headers) {
              request.setRequestHeader(name, headers[name]);
          }
      }
docs: Adds the configured additional headers to the given request.
  
  @param {XMLHttpRequest} request
  The request where the configured extra headers will be added.
  
  @param {Object} headers
  The headers to be added to the request.
  
  @private