The Tor Browser / file revision

 function getter() { return 1; }

 function setter() { }

 function getDescriptor(name) {

   if (name != 'prop')

     throw "Unknown property: " + name;

   return { configurable: true, enumerable: true, get: getter, set: setter };

 }

 function getNames() { return ['prop']; }

 var handler = {

   getOwnPropertyDescriptor: getDescriptor,

   getPropertyDescriptor: getDescriptor,

   getOwnPropertyNames: getNames,

   getPropertyNames: getNames,

   defineProperty: function() {},

   delete: function() {}

 };

 // Make sure that __lookup{Getter,Setter}__ works on proxies.

 var proxy = Proxy.create(handler);

 assertEq(Object.prototype.__lookupGetter__.call(proxy, 'prop'), getter);

 assertEq(Object.prototype.__lookupSetter__.call(proxy, 'prop'), setter);