Only change timeout to 100ms after the connection is established.

tests/standalone/io/http_server_idle_timeout_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.
 //
 // VMOptions=
 // VMOptions=--short_socket_read
 // VMOptions=--short_socket_write
 // VMOptions=--short_socket_read --short_socket_write
 
-import "package:expect/expect.dart";
 import "dart:async";
 import "dart:io";
 import "dart:isolate";
 
 
 void testTimeoutAfterRequest() {
   HttpServer.bind("127.0.0.1", 0).then((server) {
-    server.idleTimeout = const Duration(milliseconds: 100);
+    server.idleTimeout = null;
 
-    server.listen((request) => request.response.close());
+    server.listen((request) {
+      server.idleTimeout = const Duration(milliseconds: 100);
+      request.response.close();
+    });
 
     Socket.connect("127.0.0.1", server.port).then((socket) {
       var data = "GET / HTTP/1.1\r\nContent-Length: 0\r\n\r\n";
       socket.write(data);
       socket.listen(
           null,
           onDone: () {
             socket.close();
             server.close();
           });
@@ skipping 15 matching lines @@
             server.close();
           });
     });
   });
 }
 
 void main() {
   testTimeoutAfterRequest();
   testTimeoutBeforeRequest();
 }