Put making embedded maps in optimized code weak behind a flag.

src/objects-visiting-inl.h

Index: src/objects-visiting-inl.h
diff --git a/src/objects-visiting-inl.h b/src/objects-visiting-inl.h
index e2b0e255bb462684a75dbed9efd297dde779c9a0..7332a0c8d6ad591df61a2e7c3195e103de1cfdf5 100644
--- a/src/objects-visiting-inl.h
+++ b/src/objects-visiting-inl.h
@@ -175,7 +175,8 @@ void StaticMarkingVisitor<StaticVisitor>::VisitEmbeddedPointer(
   ASSERT(rinfo->rmode() == RelocInfo::EMBEDDED_OBJECT);
   ASSERT(!rinfo->target_object()->IsConsString());
   HeapObject* object = HeapObject::cast(rinfo->target_object());
-  if (!FLAG_collect_maps || rinfo->host()->kind() != Code::OPTIMIZED_FUNCTION ||
+  if (!FLAG_weak_embedded_maps_in_optimized_code ||
+      !FLAG_collect_maps || rinfo->host()->kind() != Code::OPTIMIZED_FUNCTION ||
       !object->IsMap() || !Map::cast(object)->CanTransition()) {
     heap->mark_compact_collector()->RecordRelocSlot(rinfo, object);
     StaticVisitor::MarkObject(heap, object);