Map::ReconfigureProperty() should mark map as unstable when it returns a different map.

src/objects-printer.cc

Index: src/objects-printer.cc
diff --git a/src/objects-printer.cc b/src/objects-printer.cc
index fb6643a2129e9619f9adf23e3ce7f4d535883b8f..8c7e9914a29f9af9326348ed370cd69d5358c87b 100644
--- a/src/objects-printer.cc
+++ b/src/objects-printer.cc
@@ -416,6 +416,7 @@ void Map::MapPrint(std::ostream& os) {  // NOLINT
      << pre_allocated_property_fields() << "\n";
   os << " - unused property fields: " << unused_property_fields() << "\n";
   if (is_deprecated()) os << " - deprecated_map\n";
+  if (is_stable()) os << " - stable_map\n";
   if (is_dictionary_map()) os << " - dictionary_map\n";
   if (is_prototype_map()) {
     os << " - prototype_map\n";