anchor.diff:               transformRequest: transformRequest, transformResponse: transformResponse,
                cache: cache, timeout: timeout);
   
  +  /**
  +   * Shortcut method for JSONP requests.  See [call] for a complete description
  +   * of parameters.
  +   */
     async.Future<HttpResponse> jsonp(String url, {
       String data,
       Map<String, dynamic> params,
  
positive.code:              transformRequest: transformRequest, transformResponse: transformResponse,
               cache: cache, timeout: timeout);
  
    async.Future<HttpResponse> head(String url, {
      String data,
      Map<String, dynamic> params,
  
negative.code: }
  
  /**
   * The [Http] service facilitates communication with the remote HTTP servers.  It
   * uses dart:html's [HttpRequest] and provides a number of features on top
   * of the core Dart library.
   *
   * For unit testing, applications should use the [MockHttpBackend] service.
   *
   * # General usage
   * The [call] method takes a number of named parameters and returns a
   * [Future<HttpResponse>].
   *
   *      http(method: 'GET', url: '/someUrl')
   *        .then((HttpResponse response) { .. },
   *               onError: (HttpRequest request) { .. });
   *
   * A response status code between 200 and 299 is considered a success status and
   * will result in the 'then' being called. Note that if the response is a redirect,
   * Dart's [HttpRequest] will transparently follow it, meaning that the error callback will not be
   * called for such responses.
   *
   * # Shortcut methods
   *
   * The Http service also defines a number of shortcuts:
   *
   *      http.get('/someUrl') is the same as http(method: 'GET', url: '/someUrl')
   *
   * See the method definitions below.
   *
   * # Setting HTTP Headers
   *
   * The [Http] service will add certain HTTP headers to requests.  These defaults
   * can be configured using the [HttpDefaultHeaders] object.  The defaults are:
   *
   * - For all requests: `Accept: application/json, text/plain, * / *`
   * - For POST, PUT, PATCH requests: `Content-Type: application/json`
   *
   * # Transforming Requests and Responses
   *
   *  NOTE: < use interceptors >.
   *
   * # Caching
   *
   * To enable caching, pass a [Cache] object into the [call] method.  The [Http]
   * service will store responses in the cache and return the response for
   * any matching requests.
   *
   * Note that data is returned through a [Future], regardless of whether it
   * came from the [Cache] or the server.
   *
   * If there are multiple GET requests for the same not-yet-in-cache URL
   * while a cache is in use, only one request to the server will be made.
   *
   * # Interceptors
   *
   * NOTE: < not yet implemented >
   *
   * # Security Considerations
   *
   * NOTE: < not yet documented >
   */
  class Http {
    Map<String, async.Future<HttpResponse>> _pendingRequests = <String, async.Future<HttpResponse>>{};
  