anchor.diff:        req.send();
       }
     }
  +
  +  static _attachCallbacks(request, options) {
  +    if (options == null) return;
  +
  +    if (options.containsKey('onLoad')) {
  +      request.on.load.add((event) {
  +        var req = event.target,
  +            json = JSON.parse(req.responseText);
  +
  +        options['onLoad'](json);
  +      });
  +    }
  +  }
   }
  
positive.code:   // forward the call to the appropriate behavior (injected or default)
    static call(method, model, [options]) {
      if (_injected_sync == null) {
        return _default_sync(method, model, options:options);
      }
      else {
        return _injected_sync(method, model, options:options);
  
negative.code:   }
  
    // default sync behavior
    static _defaultSync(method, model, [options]) {
      var req = new XMLHttpRequest();
  
      _attachCallbacks(req, options);
  
      req.open(method, model.url, true);
  
      // POST and PUT HTTP request bodies if necessary
      if (method == 'post' || method == 'put') {
        req.setRequestHeader('Content-type', 'application/json');
        req.send(JSON.stringify(model.attributes));
  