Revert "Remove Expect from core library."

tests/standalone/io/secure_socket_bad_certificate_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_write --short_socket_read
 // The --short_socket_write option does not work with external server
 // www.google.dk.  Add this to the test when we have secure server sockets.
 // See TODO below.
 
-import "package:expect/expect.dart";
 import "dart:async";
 import "dart:isolate";
 import "dart:io";
 
 void main() {
   ReceivePort keepAlive = new ReceivePort();
   SecureSocket.initialize(useBuiltinRoots: false);
   testCertificateCallback(host: "www.google.dk",
                           acceptCertificate: false).then((_) {
     testCertificateCallback(host: "www.google.dk",
@@ skipping 30 matching lines @@
         socket.close();
         return socket.reduce(<int>[], (message, data)  => message..addAll(data))
             .then((message) {
               String received = new String.fromCharCodes(message);
               Expect.isTrue(received.contains('</body></html>'));
             });
       }).catchError((e) {
         Expect.isFalse(acceptCertificate);
       });
 }