Revert "Remove Expect from core library."

tests/language/typedef_is_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";
-
 // Test is-test of typedefs with optional and named parameters.
 
 typedef int Func1(int a);
 typedef int Func2(int a, [int b]);
 typedef int Func3(int a, [int b, int c]);
 typedef int Func4([int a, int b, int c]);
 typedef int Func5(int a, {int b});
 typedef int Func6(int a, {int b, int c});
 typedef int Func7({int a, int b, int c});
 
@@ skipping 99 matching lines @@
 
   int func12({int c, int a, int b}) {}
   Expect.isFalse(func12 is Func1);
   Expect.isFalse(func12 is Func2);
   Expect.isFalse(func12 is Func3);
   Expect.isFalse(func12 is Func4);
   Expect.isFalse(func12 is Func5);
   Expect.isFalse(func12 is Func6);
   Expect.isTrue(func12 is Func7);
 }