Implement subtype relation for kernel based elements.

pkg/compiler/lib/src/resolution/registry.dart

 // Copyright (c) 2014, 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 dart2js.resolution.registry;
 
 import '../common.dart';
 import '../common/backend_api.dart' show ForeignResolver, NativeRegistry;
 import '../common/resolution.dart' show ResolutionImpact, Target;
 import '../constants/expressions.dart';
@@ skipping 129 matching lines @@
     }
     if (_constantLiterals != null) {
       sb.write('\n const-literals:');
       for (ConstantExpression constant in _constantLiterals) {
         sb.write('\n  ${constant.toDartText()}');
       }
     }
     if (_constSymbolNames != null) {
       sb.write('\n const-symbol-names: $_constSymbolNames');
     }
+    if (_nativeData != null) {
+      sb.write('\n native-data:');
+      for (var data in _nativeData) {
+        sb.write('\n  $data');
+      }
+    }
     return sb.toString();
   }
 }
 
 /// [ResolutionRegistry] collects all resolution information. It stores node
 /// related information in a [TreeElements] mapping and registers calls with
 /// [Backend], [World] and [Enqueuer].
 // TODO(johnniwinther): Split this into an interface and implementation class.
 class ResolutionRegistry {
   final Target target;
@@ skipping 271 matching lines @@
   @override
   void registerInstantiatedType(ResolutionInterfaceType type) {
     registry.registerInstantiation(type);
   }
 
   @override
   ResolutionDartType resolveTypeFromString(Node node, String typeName) {
     return visitor.resolveTypeFromString(node, typeName);
   }
 }