feat(http): xhr error listener invokes onError - #2667

    this._xhr.addEventListener('error', (err) => {
      var responseOptions = new ResponseOptions({body: err, type: ResponseTypes.Error});
      if (isPresent(baseResponseOptions)) {
        responseOptions = baseResponseOptions.merge(responseOptions);
      }
      ObservableWrapper.callThrow(this.response, new Response(responseOptions))
    });