the idea is that often times in code, you will see something like this:...

src/heap.h

Index: src/heap.h
===================================================================
--- src/heap.h	(revision 3015)
+++ src/heap.h	(working copy)
@@ -554,7 +554,9 @@
   // Returns Failure::RetryAfterGC(requested_bytes, space) if the allocation
   // failed.
   // Please note this does not perform a garbage collection.
-  static Object* AllocateConsString(String* first, String* second);
+  static Object* AllocateConsString(String* first,
+                                    String* second,
+                                    PretenureFlag pretenure = NOT_TENURED);
 
   // Allocates a new sliced string object which is a slice of an underlying
   // string buffer stretching from the index start (inclusive) to the index