[runtime] Use PropertyKind/PropertyLocation instead of PropertyType.

src/json-stringifier.cc

Index: src/json-stringifier.cc
diff --git a/src/json-stringifier.cc b/src/json-stringifier.cc
index 29685c20e22b6eadceca8ea0eba12f668aa7035f..b91b57142aac0e1f1238320cc111b7a1163e3249 100644
--- a/src/json-stringifier.cc
+++ b/src/json-stringifier.cc
@@ -534,7 +534,8 @@ JsonStringifier::Result JsonStringifier::SerializeJSObject(
       PropertyDetails details = map->instance_descriptors()->GetDetails(i);
       if (details.IsDontEnum()) continue;
       Handle<Object> property;
-      if (details.type() == DATA && *map == js_obj->map()) {
+      if (details.location() == kField && *map == js_obj->map()) {
+        DCHECK_EQ(kData, details.kind());
         FieldIndex field_index = FieldIndex::ForDescriptor(*map, i);
         property = JSObject::FastPropertyAt(js_obj, details.representation(),
                                             field_index);