Remove Expect from core library.

tests/compiler/dart2js/metadata_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";
 import "dart:uri";
 
 import 'compiler_helper.dart';
 import 'parser_helper.dart';
 
 import '../../../sdk/lib/_internal/compiler/implementation/elements/elements.dart';
 import '../../../sdk/lib/_internal/compiler/implementation/dart2jslib.dart';
 import '../../../sdk/lib/_internal/compiler/implementation/util/util.dart'
     show Spannable, Link;
 import '../../../sdk/lib/_internal/compiler/implementation/tree/tree.dart'
@@ skipping 196 matching lines @@
   compileAndCheckLibrary(source,
                          (e) => e.compilationUnits.first.partTag.metadata);
 }
 
 void main() {
   testClassMetadata();
   testTopLevelMethodMetadata();
   testTopLevelFieldMetadata();
   testLibraryTags();
 }