Remove Expect from core library.

tests/standalone/io/raw_socket_write_destroy_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";
 const SERVER_ADDRESS = "127.0.0.1";
 
 void testWriteDestroyServer() {
   int WROTE = 100000;
   RawServerSocket.bind(SERVER_ADDRESS).then((server) {
     server.listen((socket) {
       socket.writeEventsEnabled = false;
@@ skipping 67 matching lines @@
       });
       write();
     });
   });
 }
 
 void main() {
   testWriteDestroyServer();
   testWriteDestroyClient();
 }