anchor.diff:  class HttpRequest extends EventTarget native "*XMLHttpRequest" {
     /**
      * Creates a URL get request for the specified `url`.
  -   *
  +   * 
      * After completing the request, the object will call the user-provided
      * [onComplete] callback.
      */
  
positive.code:   final String responseText;
  
    /**
     * [String] telling the server the desired response format.
     *
     * Default is `String`.
     * Other options are one of 'arraybuffer', 'blob', 'document', 'json',
  
negative.code: 
    /**
     * Retrieve all the response headers from a request.
     * 
     * `null` if no headers have been received. For multipart requests,
     * `getAllResponseHeaders` will return the response headers for the current
     * part of the request.
     * 
     * See also [HTTP response headers](http://en.wikipedia.org/wiki/List_of_HTTP_header_fields#Responses)
     * for a list of common response headers.
     */
  