Make elements/names.dart its own library

tests/compiler/dart2js/patch_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 'dart:async';
 import 'package:expect/expect.dart';
 import 'package:async_helper/async_helper.dart';
 import 'package:compiler/src/compiler.dart';
 import 'package:compiler/src/diagnostics/messages.dart' show MessageKind;
 import 'package:compiler/src/elements/elements.dart';
 import 'package:compiler/src/elements/modelx.dart';
+import 'package:compiler/src/elements/names.dart';
 import 'package:compiler/src/tree/tree.dart';
 import 'package:compiler/src/types/types.dart';
 import 'package:compiler/src/universe/call_structure.dart' show CallStructure;
 import 'package:compiler/src/universe/selector.dart' show Selector;
 import 'package:compiler/src/world.dart';
 
 import 'mock_compiler.dart';
 import 'mock_libraries.dart';
 
 Future<Compiler> applyPatch(String script, String patch,
@@ skipping 1078 matching lines @@
     await testPatchNonFunction();
 
     await testPatchAndSelector();
 
     await testEffectiveTarget();
 
     await testAnalyzeAllInjectedMembers();
     await testTypecheckPatchedMembers();
   });
 }