$OpenBSD$

index 855c82c..21a05e6 100644
--- dom/bindings/DOMJSProxyHandler.cpp.orig	Fri Feb 20 15:40:37 2015
+++ dom/bindings/DOMJSProxyHandler.cpp	Fri Feb 20 15:40:37 2015
@@ -188,6 +188,16 @@ BaseDOMProxyHandler::getPropertyDescriptor(JSContext* cx,
 }
 
 bool
+BaseDOMProxyHandler::getOwnPropertyDescriptor(JSContext* cx,
+                                              JS::Handle<JSObject*> proxy,
+                                              JS::Handle<jsid> id,
+                                              MutableHandle<JSPropertyDescriptor> desc)
+{
+  return getOwnPropDescriptor(cx, proxy, id, /* ignoreNamedProps = */ false,
+                              desc);
+}
+
+bool
 DOMProxyHandler::defineProperty(JSContext* cx, JS::Handle<JSObject*> proxy, JS::Handle<jsid> id,
                                 MutableHandle<JSPropertyDescriptor> desc, bool* defined)
 {
@@ -225,7 +235,30 @@ DOMProxyHandler::set(JSContext *cx, Handle<JSObject*> proxy, Handle<JSObject*> r
   if (done) {
     return true;
   }
-  return mozilla::dom::BaseDOMProxyHandler::set(cx, proxy, receiver, id, strict, vp);
+
+  // Make sure to ignore our named properties when checking for own
+  // property descriptors for a set.
+  JS::Rooted<JSPropertyDescriptor> desc(cx);
+  if (!getOwnPropDescriptor(cx, proxy, id, /* ignoreNamedProps = */ true,
+                            &desc)) {
+    return false;
+  }
+  bool descIsOwn = desc.object() != nullptr;
+  if (!desc.object()) {
+    // Don't just use getPropertyDescriptor, unlike BaseProxyHandler::set,
+    // because that would call getOwnPropertyDescriptor on ourselves.  Instead,
+    // directly delegate to the proto, if any.
+    JS::Rooted<JSObject*> proto(cx);
+    if (!js::GetObjectProto(cx, proxy, &proto)) {
+      return false;
+    }
+    if (proto && !JS_GetPropertyDescriptorById(cx, proto, id, &desc)) {
+      return false;
+    }
+  }
+
+  return js::SetPropertyIgnoringNamedGetter(cx, this, proxy, receiver, id,
+                                            &desc, descIsOwn, strict, vp);
 }
 
 bool