Make elements/names.dart its own library

tests/compiler/dart2js/jsinterop/world_test.dart

 // Copyright (c) 2016, 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 jsinterop.world_test;
 
 import 'package:expect/expect.dart';
 import 'package:async_helper/async_helper.dart';
 import 'package:compiler/src/common.dart';
-import 'package:compiler/src/elements/elements.dart'
-    show ClassElement, PublicName;
+import 'package:compiler/src/elements/elements.dart' show ClassElement;
+import 'package:compiler/src/elements/names.dart';
 import 'package:compiler/src/js_backend/js_backend.dart';
 import 'package:compiler/src/universe/selector.dart';
 import 'package:compiler/src/world.dart';
 import '../type_test_helper.dart';
 
 void main() {
   asyncTest(() async {
     await testClasses();
   });
 }
@@ skipping 177 matching lines @@
 
   await test('main() => newE();', directlyInstantiated: ['E']);
 
   await test('main() => newF();', directlyInstantiated: ['F']);
 
   await test('main() => [newD(), newE()];',
       directlyInstantiated: ['E'],
       abstractlyInstantiated: ['A', 'B', 'C', 'D'],
       indirectlyInstantiated: ['Object', 'Interceptor', 'JavaScriptObject']);
 }