diff -r 370ea18e73f5 js/src/jsproxy.cpp
--- a/js/src/jsproxy.cpp	Mon Apr 23 22:28:15 2012 -0400
+++ b/js/src/jsproxy.cpp	Mon Apr 23 23:46:06 2012 -0400
@@ -385,16 +385,93 @@ ProxyHandler::finalize(JSFreeOp *fop, JS
 {
 }
 
 void
 ProxyHandler::trace(JSTracer *trc, JSObject *proxy)
 {
 }
 
+AbstractProxyHandler::AbstractProxyHandler(void *family) : ProxyHandler(family)
+{
+}
+
+bool
+AbstractProxyHandler::getPropertyDescriptor(JSContext *cx, JSObject *proxy,
+                                            jsid id, bool set,
+                                            PropertyDescriptor *desc)
+{
+    return JS_GetPropertyDescriptorById(cx, GetProxyTargetObject(proxy), id,
+                                        JSRESOLVE_QUALIFIED, desc);
+}
+
+static bool
+GetOwnPropertyDescriptor(JSContext *cx, JSObject *obj, jsid id, unsigned flags,
+                         JSPropertyDescriptor *desc)
+{
+    // If obj is a proxy, we can do better than just guessing. This is
+    // important for certain types of wrappers that wrap other wrappers.
+    if (obj->isProxy())
+        return Proxy::getOwnPropertyDescriptor(cx, obj, id,
+                                               flags & JSRESOLVE_ASSIGNING,
+                                               desc);
+
+    if (!JS_GetPropertyDescriptorById(cx, obj, id, flags, desc))
+        return false;
+    if (desc->obj != obj)
+        desc->obj = NULL;
+    return true;
+}
+
+bool
+AbstractProxyHandler::getOwnPropertyDescriptor(JSContext *cx, JSObject *proxy,
+                                               jsid id, bool set,
+                                               PropertyDescriptor *desc)
+{
+    return GetOwnPropertyDescriptor(cx, GetProxyTargetObject(proxy), id,
+                                    JSRESOLVE_QUALIFIED, desc);
+}
+
+bool
+AbstractProxyHandler::defineProperty(JSContext *cx, JSObject *proxy, jsid id,
+                                     PropertyDescriptor *desc)
+{
+    return JS_DefinePropertyById(cx, GetProxyTargetObject(proxy), id,
+                                 desc->value, desc->getter, desc->setter,
+                                 desc->attrs);
+}
+
+bool
+AbstractProxyHandler::getOwnPropertyNames(JSContext *cx, JSObject *proxy,
+                                          AutoIdVector &props)
+{
+    return GetPropertyNames(cx, GetProxyTargetObject(proxy),
+                            JSITER_OWNONLY | JSITER_HIDDEN, &props);
+}
+
+bool
+AbstractProxyHandler::delete_(JSContext *cx, JSObject *proxy, jsid id, bool *bp)
+{
+    Value v;
+    if (!JS_DeletePropertyById2(cx, GetProxyTargetObject(proxy), id, &v))
+        return false;
+    JSBool b;
+    if (!JS_ValueToBoolean(cx, v, &b))
+        return false;
+    *bp = !!b;
+    return true;
+}
+
+bool
+AbstractProxyHandler::enumerate(JSContext *cx, JSObject *proxy,
+                                AutoIdVector &props)
+{
+    return GetPropertyNames(cx, GetProxyTargetObject(proxy), 0, &props);
+}
+
 static bool
 GetTrap(JSContext *cx, JSObject *handler, JSAtom *atom, Value *fvalp)
 {
     JS_CHECK_RECURSION(cx, return false);
 
     return handler->getGeneric(cx, ATOM_TO_JSID(atom), fvalp);
 }
 
diff -r 370ea18e73f5 js/src/jsproxy.h
--- a/js/src/jsproxy.h	Mon Apr 23 22:28:15 2012 -0400
+++ b/js/src/jsproxy.h	Mon Apr 23 23:46:06 2012 -0400
@@ -95,16 +95,34 @@ class JS_FRIEND_API(ProxyHandler) {
         return false;
     }
 
     inline void *family() {
         return mFamily;
     }
 };
 
+class JS_PUBLIC_API(AbstractProxyHandler) : public ProxyHandler {
+public:
+    explicit AbstractProxyHandler(void *family);
+
+    /* ES5 Harmony fundamental proxy traps. */
+    virtual bool getPropertyDescriptor(JSContext *cx, JSObject *proxy, jsid id,
+                                       bool set, PropertyDescriptor *desc);
+    virtual bool getOwnPropertyDescriptor(JSContext *cx, JSObject *proxy,
+                                          jsid id, bool set,
+                                          PropertyDescriptor *desc);
+    virtual bool defineProperty(JSContext *cx, JSObject *proxy, jsid id,
+                                PropertyDescriptor *desc);
+    virtual bool getOwnPropertyNames(JSContext *cx, JSObject *proxy,
+                                     AutoIdVector &props);
+    virtual bool delete_(JSContext *cx, JSObject *proxy, jsid id, bool *bp);
+    virtual bool enumerate(JSContext *cx, JSObject *proxy, AutoIdVector &props);
+};
+
 /* Dispatch point for handlers that executes the appropriate C++ or scripted traps. */
 class Proxy {
   public:
     /* ES5 Harmony fundamental proxy traps. */
     static bool getPropertyDescriptor(JSContext *cx, JSObject *proxy, jsid id, bool set,
                                       PropertyDescriptor *desc);
     static bool getPropertyDescriptor(JSContext *cx, JSObject *proxy, jsid id, bool set, Value *vp);
     static bool getOwnPropertyDescriptor(JSContext *cx, JSObject *proxy, jsid id, bool set,
@@ -185,16 +203,23 @@ GetProxyHandler(const JSObject *obj)
 
 inline const Value &
 GetProxyPrivate(const JSObject *obj)
 {
     JS_ASSERT(IsProxy(obj));
     return GetReservedSlot(obj, JSSLOT_PROXY_PRIVATE);
 }
 
+inline JSObject *
+GetProxyTargetObject(const JSObject *obj)
+{
+    JS_ASSERT(IsProxy(obj));
+    return GetProxyPrivate(obj).toObjectOrNull();
+}
+
 inline const Value &
 GetProxyExtra(const JSObject *obj, size_t n)
 {
     JS_ASSERT(IsProxy(obj));
     return GetReservedSlot(obj, JSSLOT_PROXY_EXTRA + n);
 }
 
 inline void