[serializer] cosmetic changes to SerializerReference.

src/snapshot/deserializer.cc

Index: src/snapshot/deserializer.cc
diff --git a/src/snapshot/deserializer.cc b/src/snapshot/deserializer.cc
index 1280750bba0ac524ee74b979e53657227d05868a..88820ae6033efe63b29c13389d6e8545b2de2a63 100644
--- a/src/snapshot/deserializer.cc
+++ b/src/snapshot/deserializer.cc
@@ -312,7 +312,8 @@ void Deserializer::CommitPostProcessedObjects(Isolate* isolate) {
 
 HeapObject* Deserializer::GetBackReferencedObject(int space) {
   HeapObject* obj;
-  SerializerReference back_reference(source_.GetInt());
+  SerializerReference back_reference =
+      SerializerReference::FromBitfield(source_.GetInt());
   if (space == LO_SPACE) {
     CHECK(back_reference.chunk_index() == 0);
     uint32_t index = back_reference.large_object_index();