Don't close existing connection on HttpServer close (and stream cancel).

tests/standalone/io/http_client_request_test.dart

 // Copyright (c) 2013, 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.
 
 import "dart:async";
 import "dart:io";
 import "dart:typed_data";
 
 import "package:async_helper/async_helper.dart";
 import "package:expect/expect.dart";
 
 void testClientRequest(Future handler(request)) {
   HttpServer.bind("127.0.0.1", 0).then((server) {
     server.listen((request) {
-      request.listen((_) {}, onDone: () {
-        request.response.close();
-      }, onError: (e) {});
+      request.drain()
+          .then((_) => request.response.close())
+          .catchError((_) {});
     });
 
     var client = new HttpClient();
     client.get("127.0.0.1", server.port, "/")
       .then((request) {
         return handler(request);
       })
-      .then((response) {
-        response.listen((_) {}, onDone: () {
-          client.close();
-          server.close();
-        });
-      })
-      .catchError((error) {
+      .then((response) => response.drain())
+      .catchError((_) {})
+      .whenComplete(() {
+        client.close();
         server.close();
-        client.close();
       });
   });
 }
 
 void testResponseDone() {
   testClientRequest((request) {
     request.close().then((res1) {
       request.done.then((res2) {
         Expect.equals(res1, res2);
       });
@@ skipping 61 matching lines @@
     }, test: (e) => e is HttpException);
     return request.done;
   });
 }
 
 void main() {
   testResponseDone();
   testBadResponseAdd();
   testBadResponseClose();
 }