Revert "Remove Expect from core library."

tests/compiler/dart2js/type_substitution_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.
 
 library type_substitution_test;
 
-import "package:expect/expect.dart";
 import '../../../sdk/lib/_internal/compiler/implementation/dart_types.dart';
 import "compiler_helper.dart";
 import "parser_helper.dart";
 import "type_test_helper.dart";
 
 DartType getType(compiler, String name) {
   var clazz = findElement(compiler, "Class");
   clazz.ensureResolved(compiler);
   var element = clazz.buildScope().lookup(buildSourceString(name));
   Expect.isNotNull(element);
@@ skipping 203 matching lines @@
       '$Typedef2_int_String.unalias=$unalias1 != $Function_int_String');
 
   DartType Typedef1 = getType(compiler, "Typedef1c");
   Expect.isNotNull(Typedef1);
   DartType Function_dynamic_dynamic = getType(compiler, "Function1c");
   Expect.isNotNull(Function_dynamic_dynamic);
   DartType unalias2 = Typedef1.unalias(compiler);
   Expect.equals(Function_dynamic_dynamic, unalias2,
       '$Typedef1.unalias=$unalias2 != $Function_dynamic_dynamic');
 }