Revert "Remove Expect from core library."

tests/standalone/io/zlib_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.
 
-import "package:expect/expect.dart";
 import 'dart:async';
 import 'dart:io';
 import 'dart:isolate';
 
 void testZLibDeflate() {
   test(int level, List<int> expected) {
     var port = new ReceivePort();
     var data = [0, 1, 2, 3, 4, 5, 6, 7, 8, 9];
     var controller = new StreamController();
     controller.stream.transform(new ZLibDeflater(gzip: false, level: level))
@@ skipping 103 matching lines @@
     test(i);
   }
 }
 
 void main() {
   testZLibDeflate();
   testZLibDeflateGZip();
   testZLibDeflateInvalidLevel();
   testZLibInflate();
 }