Revert "Remove Expect from core library."

tests/lib/async/stream_transform_test.dart

 // Copyright (c) 2011, 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.
 
 library stream_transform_test;
 
-import "package:expect/expect.dart";
 import 'dart:async';
 import '../../../pkg/unittest/lib/unittest.dart';
 import 'event_helper.dart';
 
 
 main() {
   // Regression tests for http://dartbug.com/8310 and 8311
 
   test("simpleDone", () {
     StreamController c = new StreamController();
@@ skipping 34 matching lines @@
     controller.stream.map((e) => e).transform(new StreamTransformer(
         handleData: (element, sink) { sink.add(element); },
         handleDone: (sink) { sink.close(); })
     ).listen(expectAsync1((e) => expect(e, equals("foo"))));
 
     controller.add("foo");
     // Should not crash.
     controller.close();
   });
 }