Fix a bug in [http.BaseRequest.send]'s content length handling.

pkg/http/lib/src/base_request.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 base_request;
 
 import 'dart:async';
 import 'dart:collection';
 
 import 'byte_stream.dart';
@@ skipping 97 matching lines @@
   /// Sends this request.
   ///
   /// This automatically initializes a new [Client] and closes that client once
   /// the request is complete. If you're planning on making multiple requests to
   /// the same server, you should use a single [Client] for all of those
   /// requests.
   Future<StreamedResponse> send() {
     var client = new Client();
     return client.send(this).then((response) {
       var stream = onDone(response.stream, client.close);
-      var contentLength = response.contentLength < 0 ?
-          null : response.contentLength;
       return new StreamedResponse(
           new ByteStream(stream),
           response.statusCode,
-          contentLength: contentLength,
+          contentLength: response.contentLength,
           request: response.request,
           headers: response.headers,
           isRedirect: response.isRedirect,
           persistentConnection: response.persistentConnection,
           reasonPhrase: response.reasonPhrase);
     }).catchError((e) {
       client.close();
       throw e;
     });
   }
 
   // Throws an error if this request has been finalized.
   void _checkFinalized() {
     if (!finalized) return;
     throw new StateError("Can't modify a finalized Request.");
   }
 
   String toString() => "$method $url";
 }