Add an interface for an embedder to provide information about native

src/objects.h

Index: src/objects.h
diff --git a/src/objects.h b/src/objects.h
index d7b87c65d72df64da143200773db08e2295fa343..241cc916b764825f2679caad8c386a0bf0014676 100644
--- a/src/objects.h
+++ b/src/objects.h
@@ -5156,6 +5156,11 @@ class StringHasher {
 };
 
 
+// Calculates string hash.
+template <typename schar>
+inline uint32_t HashSequentialString(const schar* chars, int length);
+
+
 // The characteristics of a string are stored in its map.  Retrieving these
 // few bits of information is moderately expensive, involving two memory
 // loads where the second is dependent on the first.  To improve efficiency
@@ -6537,6 +6542,9 @@ class ObjectVisitor BASE_EMBEDDED {
     VisitExternalReferences(p, p + 1);
   }
 
+  // Visits a handle that has an embedder-assigned class ID.
+  virtual void VisitEmbedderReference(Object** p, uint16_t class_id) {}
+
 #ifdef DEBUG
   // Intended for serialization/deserialization checking: insert, or
   // check for the presence of, a tag at this position in the stream.