Adding JRecord and boxing mechanics

pkg/compiler/lib/src/kernel/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 '../closure.dart';
 import '../common.dart';
 import '../constants/values.dart';
 import '../common_elements.dart';
@@ skipping 226 matching lines @@
   ir.Node get node;
 
   /// The canonical location of [member]. This is used for sorting the members
   /// in the emitted code.
   SourceSpan get location;
 }
 
 enum ClassKind {
   regular,
   closure,
+  // TODO(efortuna, johnniwinther): Container is not a class, but is
+  // masquerading as one currently for consistency with the old element model.
+  record,
 }
 
 /// A member directly defined by its [ir.Member] node.
 class RegularMemberDefinition implements MemberDefinition {
   final MemberEntity member;
   final ir.Member node;
 
   RegularMemberDefinition(this.member, this.node);
 
   SourceSpan get location => computeSourceSpanFromTreeNode(node);
@@ skipping 200 matching lines @@
       uri = Uri.parse(node.location.file);
       break;
     }
     node = node.parent;
   }
   if (uri != null) {
     return new SourceSpan(uri, offset, offset + 1);
   }
   return null;
 }