Use analyzer's sealed type list

lib/src/checker/resolver.dart

Index: lib/src/checker/resolver.dart
diff --git a/lib/src/checker/resolver.dart b/lib/src/checker/resolver.dart
index 3542ad4d9d5dd64a92acb36d8515246184e7c733..427baf3575f9516954cbb781d8016b0608206271 100644
--- a/lib/src/checker/resolver.dart
+++ b/lib/src/checker/resolver.dart
@@ -560,21 +560,8 @@ class RestrictedStaticTypeAnalyzer extends StaticTypeAnalyzer {
     }
   }
 
-  List<DartType> _sealedTypes = null;
-
   bool _isSealed(DartType t) {
-    if (_sealedTypes == null) {
-      // TODO(vsm): Use the analyzer's list - see dartbug.com/23125.
-      _sealedTypes = <DartType>[
-        _typeProvider.nullType,
-        _typeProvider.numType,
-        _typeProvider.intType,
-        _typeProvider.doubleType,
-        _typeProvider.boolType,
-        _typeProvider.stringType
-      ];
-    }
-    return _sealedTypes.contains(t);
+    return _typeProvider.nonSubtypableTypes.contains(t);
   }
 
   @override // to propagate types to identifiers