Pretenure ASCII cons string in high promotion mode.

src/heap.cc

 // Copyright 2012 the V8 project authors. All rights reserved.
 // Redistribution and use in source and binary forms, with or without
 // modification, are permitted provided that the following conditions are
 // met:
 //
 //     * Redistributions of source code must retain the above copyright
 //       notice, this list of conditions and the following disclaimer.
 //     * Redistributions in binary form must reproduce the above
 //       copyright notice, this list of conditions and the following
 //       disclaimer in the documentation and/or other materials provided
@@ skipping 3158 matching lines @@
     // number string cache.
     AllocateFullSizeNumberStringCache();
     return;
   }
   number_string_cache()->set(hash * 2, number);
   number_string_cache()->set(hash * 2 + 1, string);
 }
 
 
 MaybeObject* Heap::NumberToString(Object* number,
-                                  bool check_number_string_cache) {
+                                  bool check_number_string_cache,
+                                  PretenureFlag pretenure) {
   isolate_->counters()->number_to_string_runtime()->Increment();
   if (check_number_string_cache) {
     Object* cached = GetNumberStringCache(number);
     if (cached != undefined_value()) {
       return cached;
     }
   }
 
   char arr[100];
   Vector<char> buffer(arr, ARRAY_SIZE(arr));
   const char* str;
   if (number->IsSmi()) {
     int num = Smi::cast(number)->value();
     str = IntToCString(num, buffer);
   } else {
     double num = HeapNumber::cast(number)->value();
     str = DoubleToCString(num, buffer);
   }
 
   Object* js_string;
-  MaybeObject* maybe_js_string = AllocateStringFromOneByte(CStrVector(str));
+  MaybeObject* maybe_js_string =
+      AllocateStringFromOneByte(CStrVector(str), pretenure);
   if (maybe_js_string->ToObject(&js_string)) {
     SetNumberStringCache(number, String::cast(js_string));
   }
   return maybe_js_string;
 }
 
 
 MaybeObject* Heap::Uint32ToString(uint32_t value,
                                   bool check_number_string_cache) {
   Object* number;
@@ skipping 4674 matching lines @@
   if (FLAG_parallel_recompilation) {
     heap_->relocation_mutex_->Lock();
 #ifdef DEBUG
     heap_->relocation_mutex_locked_by_optimizer_thread_ =
         heap_->isolate()->optimizing_compiler_thread()->IsOptimizerThread();
 #endif  // DEBUG
   }
 }
 
 } }  // namespace v8::internal