Keep around a copy of the http.Request that triggered each Response.

pkg/http/lib/src/streamed_response.dart

 // Copyright (c) 2012, the Dart project authors.  Please see the AUTHORS file
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
 library streamed_response;
 
 import 'dart:io';
 
 import 'base_response.dart';
+import 'base_request.dart';
 
 /// An HTTP response where the response body is received asynchronously after
 /// the headers have been received.
 class StreamedResponse extends BaseResponse {
   /// The stream from which the response body data can be read.
   final InputStream stream;
 
   /// Creates a new streaming response.
   StreamedResponse(
       this.stream,
       int statusCode,
       int contentLength,
-      {Map<String, String> headers: const <String>{},
+      {BaseRequest request,
+       Map<String, String> headers: const <String>{},
        bool isRedirect: false,
        bool persistentConnection: true,
        String reasonPhrase})
     : super(
         statusCode,
         contentLength,
+        request: request,
         headers: headers,
         isRedirect: isRedirect,
         persistentConnection: persistentConnection,
         reasonPhrase: reasonPhrase);
 }