Revert "Remove Expect from core library."

tests/language/function_type_alias4_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.
 //
 // Dart test for function type alias with a type parameter as result type.
 
-import "package:expect/expect.dart";
-
 typedef bool F<bool>(bool a);  // 'bool' is not the boolean type.
 
 bool bar(bool a) {
 }
 
 int baz(int a) {
 }
 
 class A<T> {
   T foo(T a) {
@@ skipping 10 matching lines @@
 
   var b = new A<bool>();
   var i = new A<int>();
   Expect.isTrue(b.foo is F);
   Expect.isTrue(i.foo is F);
   Expect.isTrue(b.foo is F<bool>);
   Expect.isTrue(i.foo is F<int>);
   Expect.isTrue(b.foo is !F<int>);
   Expect.isTrue(i.foo is !F<bool>);
 }