Pretenure ASCII cons string in high promotion mode.

src/runtime.cc

Index: src/runtime.cc
diff --git a/src/runtime.cc b/src/runtime.cc
index 8cd2de21b6c7513752456a06b374a8246cc4cb8e..c26c0596929f3ccf68323edd4b7e026c52ed144a 100644
--- a/src/runtime.cc
+++ b/src/runtime.cc
@@ -234,7 +234,9 @@ static Handle<Object> CreateObjectLiteralBoilerplate(
                                 constant_properties,
                                 &is_result_from_cache);
 
-  Handle<JSObject> boilerplate = isolate->factory()->NewJSObjectFromMap(map);
+  Handle<JSObject> boilerplate =
+      isolate->factory()->NewJSObjectFromMap(
+          map, isolate->heap()->GetPretenureMode());
 
   // Normalize the elements of the boilerplate to save space if needed.
   if (!should_have_fast_elements) JSObject::NormalizeElements(boilerplate);
@@ -338,8 +340,10 @@ Handle<Object> Runtime::CreateArrayLiteralBoilerplate(
   // Create the JSArray.
   Handle<JSFunction> constructor(
       JSFunction::NativeContextFromLiterals(*literals)->array_function());
-  Handle<JSArray> object =
-      Handle<JSArray>::cast(isolate->factory()->NewJSObject(constructor));
+
+  Handle<JSArray> object = Handle<JSArray>::cast(
+      isolate->factory()->NewJSObject(
+          constructor, isolate->heap()->GetPretenureMode()));
 
   ElementsKind constant_elements_kind =
       static_cast<ElementsKind>(Smi::cast(elements->get(0))->value());
@@ -6131,7 +6135,8 @@ RUNTIME_FUNCTION(MaybeObject*, Runtime_NumberToStringSkipCache) {
   Object* number = args[0];
   RUNTIME_ASSERT(number->IsNumber());
 
-  return isolate->heap()->NumberToString(number, false);
+  return isolate->heap()->NumberToString(
+      number, false, isolate->heap()->GetPretenureMode());
 }