Properly load transition target descriptor info

src/objects.cc

Index: src/objects.cc
diff --git a/src/objects.cc b/src/objects.cc
index aa870e0cff516eec113cae8a72a3926795ca864f..0c943c7941a1346f92e53fc22d78691f4b66172a 100644
--- a/src/objects.cc
+++ b/src/objects.cc
@@ -3880,9 +3880,9 @@ MaybeObject* JSObject::SetPropertyForResult(LookupResult* lookup,
                   lookup->holder()->MigrateToMap(Map::cast(back));
               if (maybe_failure->IsFailure()) return maybe_failure;
             }
-            DescriptorArray* desc = transition_map->instance_descriptors();
-            int descriptor = transition_map->LastAdded();
-            representation = desc->GetDetails(descriptor).representation();
+            descriptors = transition_map->instance_descriptors();
+            representation =
+                descriptors->GetDetails(descriptor).representation();
           }
           int field_index = descriptors->GetFieldIndex(descriptor);
           result = lookup->holder()->AddFastPropertyUsingMap(
@@ -4085,9 +4085,9 @@ MaybeObject* JSObject::SetLocalPropertyIgnoreAttributes(
               MaybeObject* maybe_failure = self->MigrateToMap(Map::cast(back));
               if (maybe_failure->IsFailure()) return maybe_failure;
             }
-            DescriptorArray* desc = transition_map->instance_descriptors();
-            int descriptor = transition_map->LastAdded();
-            representation = desc->GetDetails(descriptor).representation();
+            descriptors = transition_map->instance_descriptors();
+            representation =
+                descriptors->GetDetails(descriptor).representation();
           }
           int field_index = descriptors->GetFieldIndex(descriptor);
           result = self->AddFastPropertyUsingMap(