anchor.diff:    }
   
     // default sync behavior
  -  static _default_sync(method, model, [options]) {
  -    print("[_default_sync]");
  -
  -    if (options == null) options = {};
  -
  +  static _defaultSync(method, model, [options]) {
       var req = new XMLHttpRequest();
   
  -    if (options.containsKey('onLoad')) {
  -      req.on.load.add((event) {
  -        var request = event.target;
  -        print(request.responseText);
  -
  -        var list = JSON.parse(request.responseText);
  -
  -        options['onLoad'](list);
  -      });
  -    }
  +    _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));
  
positive.code:       req.send();
      }
    }
  }
  
negative.code:   // forward the call to the appropriate behavior (injected or default)
    static call(method, model, [options]) {
      if (_injected_sync == null) {
        return _defaultSync(method, model, options:options);
      }
      else {
        return _injected_sync(method, model, options:options);
  