The Tor Browser / file revision

 /*

  * Any copyright is dedicated to the Public Domain.

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

  */

 /* A stock watcher function. */

 var watcherCount;

 function watcher(id, old, newval) {

     watcherCount++;

     return newval; 

 }

 /* Create an object with a value property. */

 var o = { w:2, x:3 };

 /*

  * Place a watchpoint on the value property. The watchpoint structure holds

  * the original JavaScript setter, and a pointer to the shape.

  */

 o.watch('x', watcher);

 /*

  * Put the object in dictionary mode, so that JSObject::putProperty will 

  * mutate its shapes instead of creating new ones.

  */

 delete o.w;

 /*

  * Replace the value property with a setter.

  */

 var setterCount;

 o.__defineSetter__('x', function() { setterCount++; });

 /*

  * Trigger the watchpoint. The watchpoint handler should run, and then the

  * setter should run.

  */

 watcherCount = setterCount = 0;

 o.x = 4;

 assertEq(watcherCount, 1);

 assertEq(setterCount, 1);

 reportCompare(true, true);