Revert "Remove Expect from core library."

tests/language/function_type_alias_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.
 // VMOptions=--enable_type_checks
 //
 // Dart test for function type alias.
 
-import "package:expect/expect.dart";
-
 typedef Fun(a, b);
 
 typedef int IntFun(a, b);
 
 typedef bool BoolFun(a, b);
 
 typedef int CompareObj(Object a, Object b);
 
 typedef int CompareInt(int a, int b);
 
@@ skipping 81 matching lines @@
     Function boundsTrue = (int arg) { };
     Function boundsFalse = (String arg) { };
     Expect.isTrue(boundsTrue is BoundsCheck<num>);
     Expect.isFalse(boundsFalse is BoundsCheck<num>);
   }
 }
 
 main() {
   FunctionTypeAliasTest.testMain();
 }