Revert "Remove Expect from core library."

tests/standalone/io/http_connection_close_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 "package:expect/expect.dart";
 import "dart:async";
 import "dart:io";
 import "dart:uri";
 
 void testHttp10Close(bool closeRequest) {
   HttpServer.bind().then((server) {
     server.listen((request) {
       request.response.close();
     });
 
@@ skipping 61 matching lines @@
   });
 }
 
 main() {
   testHttp10Close(false);
   testHttp10Close(true);
   testHttp11Close(false);
   testHttp11Close(true);
   testStreamResponse();
 }