Remove Expect from core library.

tests/standalone/io/http_connection_close_test.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.
 //
 
+import "package:expect/expect.dart";
 import "dart:async";
 import "dart:io";
 import "dart:uri";
 
 void testHttp10Close(bool closeRequest) {
   HttpServer server = new HttpServer();
   server.listen("127.0.0.1", 0, backlog: 5);
 
   Socket socket = new Socket("127.0.0.1", server.port);
   socket.onConnect = () {
@@ skipping 62 matching lines @@
   connection.onError = (e) => Expect.isTrue(e is HttpException);
 }
 
 main() {
   testHttp10Close(false);
   testHttp10Close(true);
   testHttp11Close(false);
   testHttp11Close(true);
   testStreamResponse();
 }