Make elements/names.dart its own library

pkg/compiler/lib/src/kernel/ir_element_map.dart

 // Copyright (c) 2017, 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:kernel/ast.dart' as ir;
 
 import '../common.dart';
 import '../common/names.dart';
 import '../constants/constructors.dart';
 import '../constants/expressions.dart';
 import '../constants/values.dart';
 import '../common_elements.dart';
 import '../elements/elements.dart';
 import '../elements/entities.dart';
+import '../elements/names.dart';
 import '../elements/operators.dart';
 import '../elements/types.dart';
 import '../js_backend/backend.dart' show JavaScriptBackend;
 import '../native/native.dart' as native;
 import '../universe/call_structure.dart';
 import '../universe/selector.dart';
 import 'kernel_debug.dart';
 
 /// Interface that translates between Kernel IR nodes and entities.
 abstract class IrToElementMap {
@@ skipping 754 matching lines @@
     }
     if (isRedirecting) {
       return new RedirectingGenerativeConstantConstructor(
           defaultValues, superConstructorInvocation);
     } else {
       return new GenerativeConstantConstructor(
           type, defaultValues, fieldMap, superConstructorInvocation);
     }
   }
 }