Virtually dispatched specialized scavengers.

src/factory.cc

Index: src/factory.cc
diff --git a/src/factory.cc b/src/factory.cc
index 39e881ac3d567b5fbdc3d354325cc62b4ea994c5..5b387413c38b0a9b95765a383cb2cdb809fa19c3 100644
--- a/src/factory.cc
+++ b/src/factory.cc
@@ -277,6 +277,8 @@ Handle<Map> Factory::CopyMap(Handle<Map> src,
   copy->set_inobject_properties(inobject_properties);
   copy->set_unused_property_fields(inobject_properties);
   copy->set_instance_size(copy->instance_size() + instance_size_delta);
+  copy->set_scavenger(Heap::GetScavenger(copy->instance_type(),
+                                         copy->instance_size()));
   return copy;
 }