Remove Expect from core library.

tests/standalone/io/pipe_server_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
 
 library ServerTest;
 
+import "package:expect/expect.dart";
 import "dart:async";
 import "dart:io";
 import "dart:isolate";
 part "testing_server.dart";
 
 
 String getDataFilename(String path) =>
     new File(path).existsSync() ? path : '../$path';
 
 
@@ skipping 92 matching lines @@
 class PipeServer extends TestingServer {
   void onConnection(Socket connection) {
     connection.pipe(connection);
   }
 }
 
 
 main() {
   PipeServerGame echoServerGame = new PipeServerGame.start();
 }