Introduce new runtime function to make join with lower memory usage.

test/mjsunit/fuzz-natives.js

 // Copyright 2008 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 100 matching lines @@
       // we don't care what happens as long as we don't crash
     }
     type++;
   }
 }
 
 var knownProblems = {
   "Abort": true,
 
   // Avoid calling the concat operation, because weird lengths
-  // may lead to out-of-memory.
+  // may lead to out-of-memory.  Ditto for StringBuilderJoin.
   "StringBuilderConcat": true,
+  "StringBuilderJoin": true,
 
   // These functions use pseudo-stack-pointers and are not robust
   // to unexpected integer values.
   "DebugEvaluate": true,
 
   // These functions do nontrivial error checking in recursive calls,
   // which means that we have to propagate errors back.
   "SetFunctionBreakPoint": true,
   "SetScriptBreakPoint": true,
   "PrepareStep": true,
@@ skipping 65 matching lines @@
     if (name in knownProblems || name in currentlyUncallable)
       continue;
     print(name);
     var argc = nativeInfo[1];
     testArgumentCount(name, argc);
     testArgumentTypes(name, argc);
   }
 }
 
 testNatives();