Issue 5071 is now fixed

tests/standalone/io/http_request_pipeling_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:io";
+import "dart:uri";
+
+void main() {
+  final int REQUEST_COUNT = 100;
+  int count = 0;
+  HttpServer.bind().then((server) {
+    server.listen((HttpRequest request) {
+      count++;
+      request.response.addString(request.uri.path);
+      request.response.close();
+      if (request.uri.path == "/done") {
+        request.response.done.then((_) {
+            Expect.equals(REQUEST_COUNT + 1, count);
+          server.close();
+        });
+      }
+    });
+    Socket.connect("127.0.0.1", server.port).then((s) {
+      s.listen((data) { });
+      for (int i = 0; i < REQUEST_COUNT; i++) {
+        s.addString("GET /$i HTTP/1.1\r\nX-Header-1: 111\r\n\r\n");
+      }
+      s.addString("GET /done HTTP/1.1\r\nConnection: close\r\n\r\n");
+      s.close();
+    });
+  });
+}