Use WeakCells in the optimized code map rather than traversing in pause.

src/factory.cc

Index: src/factory.cc
diff --git a/src/factory.cc b/src/factory.cc
index 7c215c865ff02e140bdf1808258f6d0ecf061e77..e3924c9a9c4ea2cd329811f92dcc9f592a7323c8 100644
--- a/src/factory.cc
+++ b/src/factory.cc
@@ -728,6 +728,8 @@ Handle<Context> Factory::NewNativeContext() {
   context->set_native_context(*context);
   context->set_js_array_maps(*undefined_value());
   context->set_errors_thrown(Smi::FromInt(0));
+  Handle<WeakCell> weak_cell = NewWeakCell(context);
+  context->set_self_weak_cell(*weak_cell);
   DCHECK(context->IsNativeContext());
   return context;
 }