Remove Expect from core library.

tests/standalone/io/http_client_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:io";
 import "dart:uri";
 import "dart:isolate";
 
 void testGoogle() {
   HttpClient client = new HttpClient();
   var conn = client.get('www.google.com', 80, '/');
 
   conn.onRequest = (HttpClientRequest request) {
     request.outputStream.close();
@@ skipping 62 matching lines @@
     port.close();  // We expect onError to be called, due to bad host name.
   };
 }
 
 void main() {
   testGoogle();
   testGoogleUrl();
   testInvalidUrl();
   testBadHostName();
 }