Do not ignore an empty context with extension when creating a scope object.

src/scopes.cc

Index: src/scopes.cc
diff --git a/src/scopes.cc b/src/scopes.cc
index d0ee8ec7f21af11758a2cb3c49dcf9f8a2aa6b18..a7ff28789f17b679eb650094bdec35cc28f744ad 100644
--- a/src/scopes.cc
+++ b/src/scopes.cc
@@ -149,12 +149,10 @@ Scope::Scope(Scope* inner_scope,
   SetDefaults(type, NULL, scope_info);
   if (!scope_info.is_null()) {
     num_heap_slots_ = scope_info_->ContextLength();
-    if (*scope_info != ScopeInfo::Empty()) {
-      language_mode_ = scope_info->language_mode();
-    }
-  } else if (is_with_scope()) {
-    num_heap_slots_ = Context::MIN_CONTEXT_SLOTS;
   }
+  // Ensure at least MIN_CONTEXT_SLOTS to indicate a materialized context.
+  num_heap_slots_ = Max(num_heap_slots_,
+                        static_cast<int>(Context::MIN_CONTEXT_SLOTS));
   AddInnerScope(inner_scope);
 }