Revert of Replace ad-hoc weakness in prototype transitions with WeakCell.

src/heap/objects-visiting-inl.h

Index: src/heap/objects-visiting-inl.h
diff --git a/src/heap/objects-visiting-inl.h b/src/heap/objects-visiting-inl.h
index 4133e22f732f2ab0815e21b8654e4a766b7138da..3ef51866b6341715e424292e44a6c68a06356cc8 100644
--- a/src/heap/objects-visiting-inl.h
+++ b/src/heap/objects-visiting-inl.h
@@ -601,8 +601,13 @@
   if (!StaticVisitor::MarkObjectWithoutPush(heap, transitions)) return;
 
   if (transitions->HasPrototypeTransitions()) {
-    StaticVisitor::VisitPointer(heap,
-                                transitions->GetPrototypeTransitionsSlot());
+    // Mark prototype transitions array but do not push it onto marking
+    // stack, this will make references from it weak. We will clean dead
+    // prototype transitions in ClearNonLiveReferences.
+    Object** slot = transitions->GetPrototypeTransitionsSlot();
+    HeapObject* obj = HeapObject::cast(*slot);
+    heap->mark_compact_collector()->RecordSlot(slot, slot, obj);
+    StaticVisitor::MarkObjectWithoutPush(heap, obj);
   }
 
   int num_transitions = TransitionArray::NumberOfTransitions(transitions);