Revert "Remove Expect from core library."

tests/standalone/io/secure_server_socket_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";
 const HOST_NAME = "localhost";
 const CERTIFICATE = "localhost_cert";
 
 void testArguments() {
   Expect.throws(() =>
@@ skipping 189 matching lines @@
   testArguments();
   testSimpleBind();
   testInvalidBind();
   testSimpleConnect(CERTIFICATE);
   testSimpleConnect("CN=localhost");
   testSimpleConnectFail("not_a_nickname");
   testSimpleConnectFail("CN=notARealDistinguishedName");
   testServerListenAfterConnect();
   testSimpleReadWrite();
 }