fix #552, Object members on native types

lib/src/compiler/nullable_type_inference.dart

Index: lib/src/compiler/nullable_type_inference.dart
diff --git a/lib/src/compiler/nullable_type_inference.dart b/lib/src/compiler/nullable_type_inference.dart
index f930333ed6fd3dbde59e14def4febf222b65e664..0cbfd4ccd728cd30ee3841a696b6c834a9617331 100644
--- a/lib/src/compiler/nullable_type_inference.dart
+++ b/lib/src/compiler/nullable_type_inference.dart
@@ -23,7 +23,7 @@ import 'element_helpers.dart' show getStaticType, isInlineJS;
 abstract class NullableTypeInference {
   LibraryElement dartCoreLibrary;
   bool isPrimitiveType(DartType type);
-  bool isObjectProperty(String name);
+  bool isObjectMember(String name);
 
   /// Known non-null local variables.
   HashSet<LocalVariableElement> _notNullLocals;
@@ -102,7 +102,7 @@ abstract class NullableTypeInference {
           return false;
         }
         // We encountered a non-Object method/property.
-        if (e != null && !isObjectProperty(e.name)) {
+        if (e != null && !isObjectMember(e.name)) {
           return false;
         }
       }