Revert "Remove Expect from core library."

tests/compiler/dart2js/type_checker_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.
 
-import "package:expect/expect.dart";
 import '../../../sdk/lib/_internal/compiler/implementation/elements/elements.dart';
 import '../../../sdk/lib/_internal/compiler/implementation/tree/tree.dart';
 import '../../../sdk/lib/_internal/compiler/implementation/util/util.dart';
 import 'mock_compiler.dart';
 import 'parser_helper.dart';
 
 import '../../../sdk/lib/_internal/compiler/implementation/elements/modelx.dart'
     show ElementX;
 
 import '../../../sdk/lib/_internal/compiler/implementation/dart2jslib.dart'
@@ skipping 738 matching lines @@
   Node node = listener.popNode();
   classElement.ensureResolved(compiler);
   TreeElements elements = compiler.resolveNodeStatement(node, classElement);
   TypeCheckerVisitor checker = new TypeCheckerVisitor(compiler, elements,
                                                                 types);
   compiler.clearWarnings();
   checker.currentClass = classElement;
   checker.analyze(node);
   compareWarningKinds(text, expectedWarnings, compiler.warnings);
 }