Revert "Remove Expect from core library."

tests/language/inline_super_test.dart

 // Copyright (c) 2012, 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.
 
 // Regression test for dart2js issue 6639.
 
 library inline_super_test;
-import "package:expect/expect.dart";
 
 part 'inline_super_part.dart';
 
 // Long comment to ensure source positions in the following code are
 // larger than the part file.  Best way to ensure that is to include
 // the part as a comment:
 //
 // class Player extends LivingActor {
 //   Player (deathCallback) : super(null, deathCallback);
 // }
 
 class Percept {}
 
 class Actor {
   final percept;
   Actor(this.percept);
 }
 
 class LivingActor extends Actor {
   // The bug occurs when inlining the node [:new Percept():] into
   // [Actor]'s constructor.  When this inlining is being initiated
   // from [Player], we must take care to ensure that we know that we
   // are inlining from this location, and not [Player].
   LivingActor () : super(new Percept());
 }
 
 main() {
   Expect.isTrue(new Player().percept is Percept);
 }