Remove Expect from core library.

tests/standalone/io/http_basic_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:isolate";
 import "dart:io";
 
 class TestServerMain {
   TestServerMain()
       : _statusPort = new ReceivePort(),
         _serverPort = null {
     _serverPort = spawnFunction(startTestServer);
   }
 
@@ skipping 290 matching lines @@
 }
 
 void main() {
   testStartStop();
   testGET();
   testPOST(true);
   testPOST(false);
   test404();
   testReasonPhrase();
 }