[strong] Refactor ObjectStrength into a replacement for strong boolean args

src/builtins.cc

Index: src/builtins.cc
diff --git a/src/builtins.cc b/src/builtins.cc
index 7ac60da66a8c579b5c620accbe9981bda99d961d..7e1e737dae2a3e0a88ed9011b7693a41ff30c147 100644
--- a/src/builtins.cc
+++ b/src/builtins.cc
@@ -989,7 +989,7 @@ BUILTIN(ArrayConcat) {
       has_double && IsFastObjectElementsKind(elements_kind)
       ? INITIALIZE_ARRAY_ELEMENTS_WITH_HOLE : DONT_INITIALIZE_ARRAY_ELEMENTS;
   Handle<JSArray> result_array = isolate->factory()->NewJSArray(
-      elements_kind, result_len, result_len, WEAK, mode);
+      elements_kind, result_len, result_len, Strength::NORMAL, mode);
   if (result_len == 0) return *result_array;
 
   int j = 0;