The Tor Browser / file revision

 /*

  * Any copyright is dedicated to the Public Domain.

  * http://creativecommons.org/licenses/publicdomain/

  */

 var hitCount;

 function watcher(p,o,n) { hitCount++; return n; }

 var a = [1];

 a.watch('length', watcher);

 hitCount = 0;

 a.length = 0;

 reportCompare(1, hitCount, "lenient; configurable: watchpoint hit");

 var b = Object.defineProperty([1],'0',{configurable:false});

 b.watch('length', watcher);

 hitCount = 0;

 var result;

 try {

     b.length = 0;    

     result = "no error";

 } catch (x) {

     result = x.toString();

 }

 reportCompare(1, hitCount, "lenient; non-configurable: watchpoint hit");

 reportCompare(1, b.length, "lenient; non-configurable: length unchanged");

 reportCompare("no error", result, "lenient; non-configurable: no error thrown");

 var c = Object.defineProperty([1],'0',{configurable:false});

 c.watch('length', watcher);

 hitCount = 0;

 var threwTypeError;

 try {

     (function(){'use strict'; c.length = 0;})();

     threwTypeError = false;

 } catch (x) {

     threwTypeError = x instanceof TypeError;

 }

 reportCompare(1, hitCount, "strict; non-configurable: watchpoint hit");

 reportCompare(1, c.length, "strict; non-configurable: length unchanged");

 reportCompare(true, threwTypeError, "strict; non-configurable: TypeError thrown");