[serializer] add options to compile eagerly and pre-age for code cache.

src/snapshot/deserializer.cc

Index: src/snapshot/deserializer.cc
diff --git a/src/snapshot/deserializer.cc b/src/snapshot/deserializer.cc
index ab5afa7f88ce1d266bd3455c44803d5ba2785c43..93a3bcb0fefa066ee50b33bae7aa2b1fe94de527 100644
--- a/src/snapshot/deserializer.cc
+++ b/src/snapshot/deserializer.cc
@@ -41,6 +41,7 @@ void Deserializer::FlushICacheForNewIsolate() {
 void Deserializer::FlushICacheForNewCodeObjects() {
   DCHECK(deserializing_user_code_);
   for (Code* code : new_code_objects_) {
+    if (FLAG_serialize_age_code) code->PreAge(isolate_);
     Assembler::FlushICache(isolate_, code->instruction_start(),
                            code->instruction_size());
   }