Revert "Remove Expect from core library."

tests/compiler/dart2js_extra/first_class_types_hashcode_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.
 
-import "package:expect/expect.dart";
-
 // Check that Type instances work with maps. This behavior is not required by
 // the specification.
 
 class A {}
 
 class B<T> {}
 
 main() {
   Map<Type, String> map = new Map<Type, String>();
   Type a = new A().runtimeType;
   Type b1 = new B<int>().runtimeType;
   Type b2 = new B<String>().runtimeType;
   map[a] = 'A';
   map[b1] = 'B<int>';
   map[b2] = 'B<String>';
   Expect.equals('A', map[new A().runtimeType]);
   Expect.equals('B<int>', map[new B<int>().runtimeType]);
   Expect.equals('B<String>', map[new B<String>().runtimeType]);
 }