Use the initial map of the Object function for empty object literals

src/hydrogen.cc

Index: src/hydrogen.cc
diff --git a/src/hydrogen.cc b/src/hydrogen.cc
index 345cce33aad85a7b6f41b20b41f38ef76fd94deb..ae63db7d538cb23f2bb463accf63ca6cd52a09ac 100644
--- a/src/hydrogen.cc
+++ b/src/hydrogen.cc
@@ -11001,7 +11001,8 @@ HInstruction* HOptimizedGraphBuilder::BuildFastLiteral(
   }
 
   // Copy in-object properties.
-  if (boilerplate_object->map()->NumberOfFields() != 0) {
+  if (boilerplate_object->map()->NumberOfFields() != 0 ||
+      boilerplate_object->map()->unused_property_fields() > 0) {
     BuildEmitInObjectProperties(boilerplate_object, object, site_context,
                                 pretenure_flag);
   }