--- a/dom/bindings/BindingUtils.cpp
+++ b/dom/bindings/BindingUtils.cpp
@@ -1808,17 +1808,17 @@ ReparentWrapper(JSContext* aCx, JS::Hand
   // return early we must avoid ending up with two reflectors pointing to the
   // same native. Other than that, the objects we create will just go away.
 
   JS::Handle<JSObject*> proto = (domClass->mGetProto)(aCx, newParent);
   if (!proto) {
     return NS_ERROR_FAILURE;
   }
 
-  JS::Rooted<JSObject*> newobj(aCx, JS_CloneObject(aCx, aObj, proto, newParent));
+  JS::Rooted<JSObject*> newobj(aCx, JS_CloneObject(aCx, aObj, proto));
   if (!newobj) {
     return NS_ERROR_FAILURE;
   }
 
   js::SetReservedOrProxyPrivateSlot(newobj, DOM_OBJECT_SLOT,
                                     js::GetReservedOrProxyPrivateSlot(aObj, DOM_OBJECT_SLOT));
 
   // At this point, both |aObj| and |newobj| point to the same native

--- a/js/src/jsfriendapi.cpp
+++ b/js/src/jsfriendapi.cpp
@@ -617,20 +617,20 @@ js::StringToLinearStringSlow(JSContext *
 
 JS_FRIEND_API(void)
 JS_SetAccumulateTelemetryCallback(JSRuntime *rt, JSAccumulateTelemetryDataCallback callback)
 {
     rt->setTelemetryCallback(rt, callback);
 }
 
 JS_FRIEND_API(JSObject *)
-JS_CloneObject(JSContext *cx, HandleObject obj, HandleObject protoArg, HandleObject parent)
+JS_CloneObject(JSContext *cx, HandleObject obj, HandleObject protoArg)
 {
     Rooted<TaggedProto> proto(cx, TaggedProto(protoArg.get()));
-    return CloneObject(cx, obj, proto, parent);
+    return CloneObject(cx, obj, proto);
 }
 
 #ifdef DEBUG
 JS_FRIEND_API(void)
 js_DumpString(JSString *str)
 {
     str->dump();
 }

--- a/js/src/jsfriendapi.h
+++ b/js/src/jsfriendapi.h
@@ -143,18 +143,17 @@ JS_ScriptHasMutedErrors(JSScript *script
 extern JS_FRIEND_API(JSObject *)
 JS_ObjectToInnerObject(JSContext *cx, JS::HandleObject obj);
 
 /* Requires obj != nullptr. */
 extern JS_FRIEND_API(JSObject *)
 JS_ObjectToOuterObject(JSContext *cx, JS::HandleObject obj);
 
 extern JS_FRIEND_API(JSObject *)
-JS_CloneObject(JSContext *cx, JS::HandleObject obj, JS::HandleObject proto,
-               JS::HandleObject parent);
+JS_CloneObject(JSContext *cx, JS::HandleObject obj, JS::HandleObject proto);
 
 /*
  * Copy the own properties of src to dst in a fast way.  src and dst must both
  * be native and must be in the compartment of cx.  They must have the same
  * class, the same parent, and the same prototype.  Class reserved slots will
  * NOT be copied.
  *
  * dst must not have any properties on it before this function is called.

--- a/js/src/jsobj.cpp
+++ b/js/src/jsobj.cpp
@@ -1772,43 +1772,43 @@ CopyProxyObject(JSContext *cx, Handle<Pr
             return false;
         SetProxyExtra(to, n, v);
     }
 
     return true;
 }
 
 JSObject *
-js::CloneObject(JSContext *cx, HandleObject obj, Handle<js::TaggedProto> proto, HandleObject parent)
+js::CloneObject(JSContext *cx, HandleObject obj, Handle<js::TaggedProto> proto)
 {
     if (!obj->isNative() && !obj->is<ProxyObject>()) {
         JS_ReportErrorNumber(cx, js_GetErrorMessage, nullptr,
                              JSMSG_CANT_CLONE_OBJECT);
         return nullptr;
     }
 
     RootedObject clone(cx);
     if (obj->isNative()) {
-        clone = NewObjectWithGivenTaggedProto(cx, obj->getClass(), proto, parent);
+        clone = NewObjectWithGivenTaggedProto(cx, obj->getClass(), proto, NullPtr());
         if (!clone)
             return nullptr;
 
         if (clone->is<JSFunction>() && (obj->compartment() != clone->compartment())) {
             JS_ReportErrorNumber(cx, js_GetErrorMessage, nullptr,
                                  JSMSG_CANT_CLONE_OBJECT);
             return nullptr;
         }
 
         if (obj->as<NativeObject>().hasPrivate())
             clone->as<NativeObject>().setPrivate(obj->as<NativeObject>().getPrivate());
     } else {
         ProxyOptions options;
         options.setClass(obj->getClass());
 
-        clone = ProxyObject::New(cx, GetProxyHandler(obj), JS::NullHandleValue, proto, parent, options);
+        clone = ProxyObject::New(cx, GetProxyHandler(obj), JS::NullHandleValue, proto, nullptr, options);
         if (!clone)
             return nullptr;
 
         if (!CopyProxyObject(cx, obj.as<ProxyObject>(), clone.as<ProxyObject>()))
             return nullptr;
     }
 
     return clone;

--- a/js/src/jsobj.h
+++ b/js/src/jsobj.h
@@ -1132,17 +1132,17 @@ CreateThisForFunctionWithProto(JSContext
 extern JSObject *
 CreateThisForFunction(JSContext *cx, js::HandleObject callee, NewObjectKind newKind);
 
 // Generic call for constructing |this|.
 extern JSObject *
 CreateThis(JSContext *cx, const js::Class *clasp, js::HandleObject callee);
 
 extern JSObject *
-CloneObject(JSContext *cx, HandleObject obj, Handle<js::TaggedProto> proto, HandleObject parent);
+CloneObject(JSContext *cx, HandleObject obj, Handle<js::TaggedProto> proto);
 
 extern NativeObject *
 DeepCloneObjectLiteral(JSContext *cx, HandleNativeObject obj, NewObjectKind newKind = GenericObject);
 
 extern bool
 DefineProperties(JSContext *cx, HandleObject obj, HandleObject props);
 
 /*