Transforming PersistentHandleVisitor to not need to copy Persistent handles.

src/api.cc

Index: src/api.cc
diff --git a/src/api.cc b/src/api.cc
index a5ef0543b5579cf87a5cba52f37bbe82c161bc16..68569a513e203e7c8b75c36e5ede2b8d45a872c7 100644
--- a/src/api.cc
+++ b/src/api.cc
@@ -5104,8 +5104,14 @@ class VisitorAdapter : public i::ObjectVisitor {
     UNREACHABLE();
   }
   virtual void VisitEmbedderReference(i::Object** p, uint16_t class_id) {
+#ifdef V8_USE_OLD_STYLE_PERSISTENT_HANDLE_VISITORS
     visitor_->VisitPersistentHandle(ToApi<Value>(i::Handle<i::Object>(p)),
                                     class_id);
+#else
+    Value* value = ToApi<Value>(i::Handle<i::Object>(p));
+    visitor_->VisitPersistentHandle(
+        reinterpret_cast<Persistent<Value>*>(&value), class_id);
+#endif
   }
  private:
   PersistentHandleVisitor* visitor_;