[snapshot] make snapshot sink a non-dynamic member of the serializer.

src/snapshot/code-serializer.h

Index: src/snapshot/code-serializer.h
diff --git a/src/snapshot/code-serializer.h b/src/snapshot/code-serializer.h
index ebe09ea1cc7292b8dd40ca1406b156145067fa7e..19489396b4641434541cfb715ecb6f6479acdc65 100644
--- a/src/snapshot/code-serializer.h
+++ b/src/snapshot/code-serializer.h
@@ -28,8 +28,8 @@ class CodeSerializer : public Serializer {
   const List<uint32_t>* stub_keys() const { return &stub_keys_; }
 
  private:
-  CodeSerializer(Isolate* isolate, SnapshotByteSink* sink, String* source)
-      : Serializer(isolate, sink), source_(source) {
+  CodeSerializer(Isolate* isolate, String* source)
+      : Serializer(isolate), source_(source) {
     reference_map_.AddAttachedReference(source);
   }