Add Smi::Zero and replace all Smi::FromInt(0) calls

src/snapshot/serializer-common.cc

Index: src/snapshot/serializer-common.cc
diff --git a/src/snapshot/serializer-common.cc b/src/snapshot/serializer-common.cc
index adfd6e4f64ee13d38a87b1b1b9cee6b00e6a6f18..baab8f3d6b26aca39cd98688b0d83def58ba0c0f 100644
--- a/src/snapshot/serializer-common.cc
+++ b/src/snapshot/serializer-common.cc
@@ -64,7 +64,7 @@ void SerializerDeserializer::Iterate(Isolate* isolate, ObjectVisitor* visitor) {
   List<Object*>* cache = isolate->partial_snapshot_cache();
   for (int i = 0;; ++i) {
     // Extend the array ready to get a value when deserializing.
-    if (cache->length() <= i) cache->Add(Smi::FromInt(0));
+    if (cache->length() <= i) cache->Add(Smi::kZero);
     // During deserialization, the visitor populates the partial snapshot cache
     // and eventually terminates the cache with undefined.
     visitor->VisitPointer(&cache->at(i));