Add m-esr52 at 52.6.0

1 files changed, 1331 insertions, 0 deletions

diff --git a/js/xpconnect/src/XPCWrappedNativeJSOps.cpp b/js/xpconnect/src/XPCWrappedNativeJSOps.cpp
new file mode 100644
index 000000000..12b203b70
--- /dev/null
+++ b/js/xpconnect/src/XPCWrappedNativeJSOps.cpp
@@ -0,0 +1,1331 @@
+/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 4 -*- */
+/* vim: set ts=8 sts=4 et sw=4 tw=99: */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+/* JavaScript JSClasses and JSOps for our Wrapped Native JS Objects. */
+
+#include "xpcprivate.h"
+#include "xpc_make_class.h"
+#include "jsprf.h"
+#include "mozilla/dom/BindingUtils.h"
+#include "mozilla/Preferences.h"
+#include "nsIAddonInterposition.h"
+#include "AddonWrapper.h"
+#include "js/Class.h"
+
+using namespace mozilla;
+using namespace JS;
+
+/***************************************************************************/
+
+// All of the exceptions thrown into JS from this file go through here.
+// That makes this a nice place to set a breakpoint.
+
+static bool Throw(nsresult errNum, JSContext* cx)
+{
+    XPCThrower::Throw(errNum, cx);
+    return false;
+}
+
+// Handy macro used in many callback stub below.
+
+#define THROW_AND_RETURN_IF_BAD_WRAPPER(cx, wrapper)                          \
+    PR_BEGIN_MACRO                                                            \
+    if (!wrapper)                                                             \
+        return Throw(NS_ERROR_XPC_BAD_OP_ON_WN_PROTO, cx);                    \
+    if (!wrapper->IsValid())                                                  \
+        return Throw(NS_ERROR_XPC_HAS_BEEN_SHUTDOWN, cx);                     \
+    PR_END_MACRO
+
+/***************************************************************************/
+
+static bool
+ToStringGuts(XPCCallContext& ccx)
+{
+    char* sz;
+    XPCWrappedNative* wrapper = ccx.GetWrapper();
+
+    if (wrapper)
+        sz = wrapper->ToString(ccx.GetTearOff());
+    else
+        sz = JS_smprintf("[xpconnect wrapped native prototype]");
+
+    if (!sz) {
+        JS_ReportOutOfMemory(ccx);
+        return false;
+    }
+
+    JSString* str = JS_NewStringCopyZ(ccx, sz);
+    JS_smprintf_free(sz);
+    if (!str)
+        return false;
+
+    ccx.SetRetVal(JS::StringValue(str));
+    return true;
+}
+
+/***************************************************************************/
+
+static bool
+XPC_WN_Shared_ToString(JSContext* cx, unsigned argc, Value* vp)
+{
+    CallArgs args = CallArgsFromVp(argc, vp);
+    RootedObject obj(cx, JS_THIS_OBJECT(cx, vp));
+    if (!obj)
+        return false;
+
+    XPCCallContext ccx(cx, obj);
+    if (!ccx.IsValid())
+        return Throw(NS_ERROR_XPC_BAD_OP_ON_WN_PROTO, cx);
+    ccx.SetName(ccx.GetContext()->GetStringID(XPCJSContext::IDX_TO_STRING));
+    ccx.SetArgsAndResultPtr(args.length(), args.array(), vp);
+    return ToStringGuts(ccx);
+}
+
+static bool
+XPC_WN_Shared_ToSource(JSContext* cx, unsigned argc, Value* vp)
+{
+    CallArgs args = CallArgsFromVp(argc, vp);
+    static const char empty[] = "({})";
+    JSString* str = JS_NewStringCopyN(cx, empty, sizeof(empty)-1);
+    if (!str)
+        return false;
+    args.rval().setString(str);
+
+    return true;
+}
+
+static bool
+XPC_WN_Shared_toPrimitive(JSContext* cx, unsigned argc, Value* vp)
+{
+    CallArgs args = CallArgsFromVp(argc, vp);
+
+    RootedObject obj(cx);
+    if (!JS_ValueToObject(cx, args.thisv(), &obj))
+        return false;
+    XPCCallContext ccx(cx, obj);
+    XPCWrappedNative* wrapper = ccx.GetWrapper();
+    THROW_AND_RETURN_IF_BAD_WRAPPER(cx, wrapper);
+
+    JSType hint;
+    if (!GetFirstArgumentAsTypeHint(cx, args, &hint))
+        return false;
+
+    if (hint == JSTYPE_NUMBER) {
+        args.rval().set(JS_GetNaNValue(cx));
+        return true;
+    }
+
+    MOZ_ASSERT(hint == JSTYPE_STRING || hint == JSTYPE_VOID);
+    ccx.SetName(ccx.GetContext()->GetStringID(XPCJSContext::IDX_TO_STRING));
+    ccx.SetArgsAndResultPtr(0, nullptr, args.rval().address());
+
+    XPCNativeMember* member = ccx.GetMember();
+    if (member && member->IsMethod()) {
+        if (!XPCWrappedNative::CallMethod(ccx))
+            return false;
+
+        if (args.rval().isPrimitive())
+            return true;
+    }
+
+    // else...
+    return ToStringGuts(ccx);
+}
+
+/***************************************************************************/
+
+// A "double wrapped object" is a user JSObject that has been wrapped as a
+// wrappedJS in order to be used by native code and then re-wrapped by a
+// wrappedNative wrapper to be used by JS code. One might think of it as:
+//    wrappedNative(wrappedJS(underlying_JSObject))
+// This is done (as opposed to just unwrapping the wrapped JS and automatically
+// returning the underlying JSObject) so that JS callers will see what looks
+// Like any other xpcom object - and be limited to use its interfaces.
+//
+// See the comment preceding nsIXPCWrappedJSObjectGetter in nsIXPConnect.idl.
+
+static JSObject*
+GetDoubleWrappedJSObject(XPCCallContext& ccx, XPCWrappedNative* wrapper)
+{
+    RootedObject obj(ccx);
+    nsCOMPtr<nsIXPConnectWrappedJS>
+        underware = do_QueryInterface(wrapper->GetIdentityObject());
+    if (underware) {
+        RootedObject mainObj(ccx, underware->GetJSObject());
+        if (mainObj) {
+            RootedId id(ccx, ccx.GetContext()->
+                            GetStringID(XPCJSContext::IDX_WRAPPED_JSOBJECT));
+
+            JSAutoCompartment ac(ccx, mainObj);
+
+            RootedValue val(ccx);
+            if (JS_GetPropertyById(ccx, mainObj, id, &val) &&
+                !val.isPrimitive()) {
+                obj = val.toObjectOrNull();
+            }
+        }
+    }
+    return obj;
+}
+
+// This is the getter native function we use to handle 'wrappedJSObject' for
+// double wrapped JSObjects.
+
+static bool
+XPC_WN_DoubleWrappedGetter(JSContext* cx, unsigned argc, Value* vp)
+{
+    CallArgs args = CallArgsFromVp(argc, vp);
+
+    RootedObject obj(cx, JS_THIS_OBJECT(cx, vp));
+    if (!obj)
+        return false;
+
+    XPCCallContext ccx(cx, obj);
+    XPCWrappedNative* wrapper = ccx.GetWrapper();
+    THROW_AND_RETURN_IF_BAD_WRAPPER(cx, wrapper);
+
+    MOZ_ASSERT(JS_TypeOfValue(cx, args.calleev()) == JSTYPE_FUNCTION, "bad function");
+
+    RootedObject realObject(cx, GetDoubleWrappedJSObject(ccx, wrapper));
+    if (!realObject) {
+        // This is pretty unexpected at this point. The object originally
+        // responded to this get property call and now gives no object.
+        // XXX Should this throw something at the caller?
+        args.rval().setNull();
+        return true;
+    }
+
+    // It is a double wrapped object. This should really never appear in
+    // content these days, but addons still do it - see bug 965921.
+    if (MOZ_UNLIKELY(!nsContentUtils::IsCallerChrome())) {
+        JS_ReportErrorASCII(cx, "Attempt to use .wrappedJSObject in untrusted code");
+        return false;
+    }
+    args.rval().setObject(*realObject);
+    return JS_WrapValue(cx, args.rval());
+}
+
+/***************************************************************************/
+
+// This is our shared function to define properties on our JSObjects.
+
+/*
+ * NOTE:
+ * We *never* set the tearoff names (e.g. nsIFoo) as JS_ENUMERATE.
+ * We *never* set toString or toSource as JS_ENUMERATE.
+ */
+
+static bool
+DefinePropertyIfFound(XPCCallContext& ccx,
+                      HandleObject obj,
+                      HandleId idArg,
+                      XPCNativeSet* set,
+                      XPCNativeInterface* ifaceArg,
+                      XPCNativeMember* member,
+                      XPCWrappedNativeScope* scope,
+                      bool reflectToStringAndToSource,
+                      XPCWrappedNative* wrapperToReflectInterfaceNames,
+                      XPCWrappedNative* wrapperToReflectDoubleWrap,
+                      XPCNativeScriptableInfo* scriptableInfo,
+                      unsigned propFlags,
+                      bool* resolved)
+{
+    RootedId id(ccx, idArg);
+    RefPtr<XPCNativeInterface> iface = ifaceArg;
+    XPCJSContext* xpccx = ccx.GetContext();
+    bool found;
+    const char* name;
+
+    propFlags |= JSPROP_RESOLVING;
+
+    if (set) {
+        if (iface)
+            found = true;
+        else
+            found = set->FindMember(id, &member, &iface);
+    } else
+        found = (nullptr != (member = iface->FindMember(id)));
+
+    if (!found) {
+        if (reflectToStringAndToSource) {
+            JSNative call;
+            uint32_t flags = 0;
+
+            if (scriptableInfo) {
+                nsCOMPtr<nsIClassInfo> classInfo = do_QueryInterface(
+                    scriptableInfo->GetCallback());
+
+                if (classInfo) {
+                    nsresult rv = classInfo->GetFlags(&flags);
+                    if (NS_FAILED(rv))
+                        return Throw(rv, ccx);
+                }
+            }
+
+            bool overwriteToString = !(flags & nsIClassInfo::DOM_OBJECT)
+                || Preferences::GetBool("dom.XPCToStringForDOMClasses", false);
+
+            if(id == xpccx->GetStringID(XPCJSContext::IDX_TO_STRING)
+                && overwriteToString)
+            {
+                call = XPC_WN_Shared_ToString;
+                name = xpccx->GetStringName(XPCJSContext::IDX_TO_STRING);
+            } else if (id == xpccx->GetStringID(XPCJSContext::IDX_TO_SOURCE)) {
+                call = XPC_WN_Shared_ToSource;
+                name = xpccx->GetStringName(XPCJSContext::IDX_TO_SOURCE);
+            } else if (id == SYMBOL_TO_JSID(
+                               JS::GetWellKnownSymbol(ccx, JS::SymbolCode::toPrimitive)))
+            {
+                call = XPC_WN_Shared_toPrimitive;
+                name = "[Symbol.toPrimitive]";
+            } else {
+                call = nullptr;
+            }
+
+            if (call) {
+                RootedFunction fun(ccx, JS_NewFunction(ccx, call, 0, 0, name));
+                if (!fun) {
+                    JS_ReportOutOfMemory(ccx);
+                    return false;
+                }
+
+                AutoResolveName arn(ccx, id);
+                if (resolved)
+                    *resolved = true;
+                RootedObject value(ccx, JS_GetFunctionObject(fun));
+                return JS_DefinePropertyById(ccx, obj, id, value,
+                                             propFlags & ~JSPROP_ENUMERATE);
+            }
+        }
+        // This *might* be a tearoff name that is not yet part of our
+        // set. Let's lookup the name and see if it is the name of an
+        // interface. Then we'll see if the object actually *does* this
+        // interface and add a tearoff as necessary.
+
+        if (wrapperToReflectInterfaceNames) {
+            JSAutoByteString name;
+            RefPtr<XPCNativeInterface> iface2;
+            XPCWrappedNativeTearOff* to;
+            RootedObject jso(ccx);
+            nsresult rv = NS_OK;
+
+            if (JSID_IS_STRING(id) &&
+                name.encodeLatin1(ccx, JSID_TO_STRING(id)) &&
+                (iface2 = XPCNativeInterface::GetNewOrUsed(name.ptr()), iface2) &&
+                nullptr != (to = wrapperToReflectInterfaceNames->
+                           FindTearOff(iface2, true, &rv)) &&
+                nullptr != (jso = to->GetJSObject()))
+
+            {
+                AutoResolveName arn(ccx, id);
+                if (resolved)
+                    *resolved = true;
+                return JS_DefinePropertyById(ccx, obj, id, jso,
+                                             propFlags & ~JSPROP_ENUMERATE);
+            } else if (NS_FAILED(rv) && rv != NS_ERROR_NO_INTERFACE) {
+                return Throw(rv, ccx);
+            }
+        }
+
+        // This *might* be a double wrapped JSObject
+        if (wrapperToReflectDoubleWrap &&
+            id == xpccx->GetStringID(XPCJSContext::IDX_WRAPPED_JSOBJECT) &&
+            GetDoubleWrappedJSObject(ccx, wrapperToReflectDoubleWrap)) {
+            // We build and add a getter function.
+            // A security check is done on a per-get basis.
+
+            JSFunction* fun;
+
+            id = xpccx->GetStringID(XPCJSContext::IDX_WRAPPED_JSOBJECT);
+            name = xpccx->GetStringName(XPCJSContext::IDX_WRAPPED_JSOBJECT);
+
+            fun = JS_NewFunction(ccx, XPC_WN_DoubleWrappedGetter,
+                                 0, 0, name);
+
+            if (!fun)
+                return false;
+
+            RootedObject funobj(ccx, JS_GetFunctionObject(fun));
+            if (!funobj)
+                return false;
+
+            propFlags |= JSPROP_GETTER | JSPROP_SHARED;
+            propFlags &= ~JSPROP_ENUMERATE;
+
+            AutoResolveName arn(ccx, id);
+            if (resolved)
+                *resolved = true;
+            return JS_DefinePropertyById(ccx, obj, id, UndefinedHandleValue, propFlags,
+                                         JS_DATA_TO_FUNC_PTR(JSNative, funobj.get()),
+                                         nullptr);
+        }
+
+        if (resolved)
+            *resolved = false;
+        return true;
+    }
+
+    if (!member) {
+        if (wrapperToReflectInterfaceNames) {
+            XPCWrappedNativeTearOff* to =
+              wrapperToReflectInterfaceNames->FindTearOff(iface, true);
+
+            if (!to)
+                return false;
+            RootedObject jso(ccx, to->GetJSObject());
+            if (!jso)
+                return false;
+
+            AutoResolveName arn(ccx, id);
+            if (resolved)
+                *resolved = true;
+            return JS_DefinePropertyById(ccx, obj, id, jso,
+                                         propFlags & ~JSPROP_ENUMERATE);
+        }
+        if (resolved)
+            *resolved = false;
+        return true;
+    }
+
+    if (member->IsConstant()) {
+        RootedValue val(ccx);
+        AutoResolveName arn(ccx, id);
+        if (resolved)
+            *resolved = true;
+        return member->GetConstantValue(ccx, iface, val.address()) &&
+               JS_DefinePropertyById(ccx, obj, id, val, propFlags);
+    }
+
+    if (scope->HasInterposition()) {
+        Rooted<PropertyDescriptor> desc(ccx);
+        if (!xpc::InterposeProperty(ccx, obj, iface->GetIID(), id, &desc))
+            return false;
+
+        if (desc.object()) {
+            AutoResolveName arn(ccx, id);
+            if (resolved)
+                *resolved = true;
+            desc.attributesRef() |= JSPROP_RESOLVING;
+            return JS_DefinePropertyById(ccx, obj, id, desc);
+        }
+    }
+
+    if (id == xpccx->GetStringID(XPCJSContext::IDX_TO_STRING) ||
+        id == xpccx->GetStringID(XPCJSContext::IDX_TO_SOURCE) ||
+        (scriptableInfo &&
+         scriptableInfo->GetFlags().DontEnumQueryInterface() &&
+         id == xpccx->GetStringID(XPCJSContext::IDX_QUERY_INTERFACE)))
+        propFlags &= ~JSPROP_ENUMERATE;
+
+    RootedValue funval(ccx);
+    if (!member->NewFunctionObject(ccx, iface, obj, funval.address()))
+        return false;
+
+    if (member->IsMethod()) {
+        AutoResolveName arn(ccx, id);
+        if (resolved)
+            *resolved = true;
+        return JS_DefinePropertyById(ccx, obj, id, funval, propFlags);
+    }
+
+    // else...
+
+    MOZ_ASSERT(member->IsAttribute(), "way broken!");
+
+    propFlags |= JSPROP_GETTER | JSPROP_SHARED;
+    propFlags &= ~JSPROP_READONLY;
+    JSObject* funobj = funval.toObjectOrNull();
+    JSNative getter = JS_DATA_TO_FUNC_PTR(JSNative, funobj);
+    JSNative setter;
+    if (member->IsWritableAttribute()) {
+        propFlags |= JSPROP_SETTER;
+        setter = JS_DATA_TO_FUNC_PTR(JSNative, funobj);
+    } else {
+        setter = nullptr;
+    }
+
+    AutoResolveName arn(ccx, id);
+    if (resolved)
+        *resolved = true;
+
+    return JS_DefinePropertyById(ccx, obj, id, UndefinedHandleValue, propFlags, getter, setter);
+}
+
+/***************************************************************************/
+/***************************************************************************/
+
+static bool
+XPC_WN_OnlyIWrite_AddPropertyStub(JSContext* cx, HandleObject obj, HandleId id, HandleValue v)
+{
+    XPCCallContext ccx(cx, obj, nullptr, id);
+    XPCWrappedNative* wrapper = ccx.GetWrapper();
+    THROW_AND_RETURN_IF_BAD_WRAPPER(cx, wrapper);
+
+    // Allow only XPConnect to add/set the property
+    if (ccx.GetResolveName() == id)
+        return true;
+
+    return Throw(NS_ERROR_XPC_CANT_MODIFY_PROP_ON_WN, cx);
+}
+
+bool
+XPC_WN_CannotModifyPropertyStub(JSContext* cx, HandleObject obj, HandleId id,
+                                HandleValue v)
+{
+    return Throw(NS_ERROR_XPC_CANT_MODIFY_PROP_ON_WN, cx);
+}
+
+bool
+XPC_WN_CantDeletePropertyStub(JSContext* cx, HandleObject obj, HandleId id,
+                              ObjectOpResult& result)
+{
+    return Throw(NS_ERROR_XPC_CANT_MODIFY_PROP_ON_WN, cx);
+}
+
+bool
+XPC_WN_CannotModifySetPropertyStub(JSContext* cx, HandleObject obj, HandleId id,
+                                   MutableHandleValue vp, ObjectOpResult& result)
+{
+    return Throw(NS_ERROR_XPC_CANT_MODIFY_PROP_ON_WN, cx);
+}
+
+bool
+XPC_WN_Shared_Enumerate(JSContext* cx, HandleObject obj)
+{
+    XPCCallContext ccx(cx, obj);
+    XPCWrappedNative* wrapper = ccx.GetWrapper();
+    THROW_AND_RETURN_IF_BAD_WRAPPER(cx, wrapper);
+
+    // Since we aren't going to enumerate tearoff names and the prototype
+    // handles non-mutated members, we can do this potential short-circuit.
+    if (!wrapper->HasMutatedSet())
+        return true;
+
+    XPCNativeSet* set = wrapper->GetSet();
+    XPCNativeSet* protoSet = wrapper->HasProto() ?
+                                wrapper->GetProto()->GetSet() : nullptr;
+
+    uint16_t interface_count = set->GetInterfaceCount();
+    XPCNativeInterface** interfaceArray = set->GetInterfaceArray();
+    for (uint16_t i = 0; i < interface_count; i++) {
+        XPCNativeInterface* iface = interfaceArray[i];
+        uint16_t member_count = iface->GetMemberCount();
+        for (uint16_t k = 0; k < member_count; k++) {
+            XPCNativeMember* member = iface->GetMemberAt(k);
+            jsid name = member->GetName();
+
+            // Skip if this member is going to come from the proto.
+            uint16_t index;
+            if (protoSet &&
+                protoSet->FindMember(name, nullptr, &index) && index == i)
+                continue;
+            if (!xpc_ForcePropertyResolve(cx, obj, name))
+                return false;
+        }
+    }
+    return true;
+}
+
+/***************************************************************************/
+
+enum WNHelperType {
+    WN_NOHELPER,
+    WN_HELPER
+};
+
+static void
+WrappedNativeFinalize(js::FreeOp* fop, JSObject* obj, WNHelperType helperType)
+{
+    const js::Class* clazz = js::GetObjectClass(obj);
+    if (clazz->flags & JSCLASS_DOM_GLOBAL) {
+        mozilla::dom::DestroyProtoAndIfaceCache(obj);
+    }
+    nsISupports* p = static_cast<nsISupports*>(xpc_GetJSPrivate(obj));
+    if (!p)
+        return;
+
+    XPCWrappedNative* wrapper = static_cast<XPCWrappedNative*>(p);
+    if (helperType == WN_HELPER)
+        wrapper->GetScriptableCallback()->Finalize(wrapper, js::CastToJSFreeOp(fop), obj);
+    wrapper->FlatJSObjectFinalized();
+}
+
+static void
+WrappedNativeObjectMoved(JSObject* obj, const JSObject* old)
+{
+    nsISupports* p = static_cast<nsISupports*>(xpc_GetJSPrivate(obj));
+    if (!p)
+        return;
+
+    XPCWrappedNative* wrapper = static_cast<XPCWrappedNative*>(p);
+    wrapper->FlatJSObjectMoved(obj, old);
+}
+
+void
+XPC_WN_NoHelper_Finalize(js::FreeOp* fop, JSObject* obj)
+{
+    WrappedNativeFinalize(fop, obj, WN_NOHELPER);
+}
+
+/*
+ * General comment about XPConnect tracing: Given a C++ object |wrapper| and its
+ * corresponding JS object |obj|, calling |wrapper->TraceSelf| will ask the JS
+ * engine to mark |obj|. Eventually, this will lead to the trace hook being
+ * called for |obj|. The trace hook should call |wrapper->TraceInside|, which
+ * should mark any JS objects held by |wrapper| as members.
+ */
+
+/* static */ void
+XPCWrappedNative::Trace(JSTracer* trc, JSObject* obj)
+{
+    const js::Class* clazz = js::GetObjectClass(obj);
+    if (clazz->flags & JSCLASS_DOM_GLOBAL) {
+        mozilla::dom::TraceProtoAndIfaceCache(trc, obj);
+    }
+    MOZ_ASSERT(IS_WN_CLASS(clazz));
+
+    XPCWrappedNative* wrapper = XPCWrappedNative::Get(obj);
+    if (wrapper && wrapper->IsValid())
+        wrapper->TraceInside(trc);
+}
+
+void
+XPCWrappedNative_Trace(JSTracer* trc, JSObject* obj)
+{
+    XPCWrappedNative::Trace(trc, obj);
+}
+
+static bool
+XPC_WN_NoHelper_Resolve(JSContext* cx, HandleObject obj, HandleId id, bool* resolvedp)
+{
+    XPCCallContext ccx(cx, obj, nullptr, id);
+    XPCWrappedNative* wrapper = ccx.GetWrapper();
+    THROW_AND_RETURN_IF_BAD_WRAPPER(cx, wrapper);
+
+    XPCNativeSet* set = ccx.GetSet();
+    if (!set)
+        return true;
+
+    // Don't resolve properties that are on our prototype.
+    if (ccx.GetInterface() && !ccx.GetStaticMemberIsLocal())
+        return true;
+
+    return DefinePropertyIfFound(ccx, obj, id,
+                                 set, nullptr, nullptr, wrapper->GetScope(),
+                                 true, wrapper, wrapper, nullptr,
+                                 JSPROP_ENUMERATE |
+                                 JSPROP_READONLY |
+                                 JSPROP_PERMANENT,
+                                 resolvedp);
+}
+
+static const js::ClassOps XPC_WN_NoHelper_JSClassOps = {
+    XPC_WN_OnlyIWrite_AddPropertyStub, // addProperty
+    XPC_WN_CantDeletePropertyStub,     // delProperty
+    nullptr,                           // getProperty
+    nullptr,                           // setProperty
+    XPC_WN_Shared_Enumerate,           // enumerate
+    XPC_WN_NoHelper_Resolve,           // resolve
+    nullptr,                           // mayResolve
+    XPC_WN_NoHelper_Finalize,          // finalize
+    nullptr,                           // call
+    nullptr,                           // construct
+    nullptr,                           // hasInstance
+    XPCWrappedNative::Trace,           // trace
+};
+
+const js::ClassExtension XPC_WN_JSClassExtension = {
+    nullptr, // weakmapKeyDelegateOp
+    WrappedNativeObjectMoved
+};
+
+const js::Class XPC_WN_NoHelper_JSClass = {
+    "XPCWrappedNative_NoHelper",
+    XPC_WRAPPER_FLAGS |
+    JSCLASS_IS_WRAPPED_NATIVE |
+    JSCLASS_PRIVATE_IS_NSISUPPORTS |
+    JSCLASS_FOREGROUND_FINALIZE,
+    &XPC_WN_NoHelper_JSClassOps,
+    JS_NULL_CLASS_SPEC,
+    &XPC_WN_JSClassExtension,
+    JS_NULL_OBJECT_OPS
+};
+
+
+/***************************************************************************/
+
+bool
+XPC_WN_MaybeResolvingPropertyStub(JSContext* cx, HandleObject obj, HandleId id, HandleValue v)
+{
+    XPCCallContext ccx(cx, obj);
+    XPCWrappedNative* wrapper = ccx.GetWrapper();
+    THROW_AND_RETURN_IF_BAD_WRAPPER(cx, wrapper);
+
+    if (ccx.GetResolvingWrapper() == wrapper)
+        return true;
+    return Throw(NS_ERROR_XPC_CANT_MODIFY_PROP_ON_WN, cx);
+}
+
+bool
+XPC_WN_MaybeResolvingSetPropertyStub(JSContext* cx, HandleObject obj, HandleId id,
+                                     MutableHandleValue vp, ObjectOpResult& result)
+{
+    result.succeed();
+    return XPC_WN_MaybeResolvingPropertyStub(cx, obj, id, vp);
+}
+
+bool
+XPC_WN_MaybeResolvingDeletePropertyStub(JSContext* cx, HandleObject obj, HandleId id,
+                                        ObjectOpResult& result)
+{
+    XPCCallContext ccx(cx, obj);
+    XPCWrappedNative* wrapper = ccx.GetWrapper();
+    THROW_AND_RETURN_IF_BAD_WRAPPER(cx, wrapper);
+
+    if (ccx.GetResolvingWrapper() == wrapper) {
+        return result.succeed();
+    }
+    return Throw(NS_ERROR_XPC_CANT_MODIFY_PROP_ON_WN, cx);
+}
+
+// macro fun!
+#define PRE_HELPER_STUB                                                       \
+    /* It's very important for "unwrapped" to be rooted here.  */             \
+    RootedObject unwrapped(cx, js::CheckedUnwrap(obj, false));                \
+    if (!unwrapped) {                                                         \
+        JS_ReportErrorASCII(cx, "Permission denied to operate on object.");   \
+        return false;                                                         \
+    }                                                                         \
+    if (!IS_WN_REFLECTOR(unwrapped)) {                                        \
+        return Throw(NS_ERROR_XPC_BAD_OP_ON_WN_PROTO, cx);                    \
+    }                                                                         \
+    XPCWrappedNative* wrapper = XPCWrappedNative::Get(unwrapped);             \
+    THROW_AND_RETURN_IF_BAD_WRAPPER(cx, wrapper);                             \
+    bool retval = true;                                                       \
+    nsresult rv = wrapper->GetScriptableCallback()->
+
+#define POST_HELPER_STUB                                                      \
+    if (NS_FAILED(rv))                                                        \
+        return Throw(rv, cx);                                                 \
+    return retval;
+
+#define POST_HELPER_STUB_WITH_OBJECTOPRESULT(failMethod)                      \
+    if (NS_FAILED(rv))                                                        \
+        return Throw(rv, cx);                                                 \
+    return retval ? result.succeed() : result.failMethod();
+
+bool
+XPC_WN_Helper_GetProperty(JSContext* cx, HandleObject obj, HandleId id,
+                          MutableHandleValue vp)
+{
+    PRE_HELPER_STUB
+    GetProperty(wrapper, cx, obj, id, vp.address(), &retval);
+    POST_HELPER_STUB
+}
+
+bool
+XPC_WN_Helper_SetProperty(JSContext* cx, HandleObject obj, HandleId id,
+                          MutableHandleValue vp, ObjectOpResult& result)
+{
+    PRE_HELPER_STUB
+    SetProperty(wrapper, cx, obj, id, vp.address(), &retval);
+    POST_HELPER_STUB_WITH_OBJECTOPRESULT(failReadOnly)
+}
+
+bool
+XPC_WN_Helper_Call(JSContext* cx, unsigned argc, Value* vp)
+{
+    JS::CallArgs args = JS::CallArgsFromVp(argc, vp);
+    // N.B. we want obj to be the callee, not JS_THIS(cx, vp)
+    RootedObject obj(cx, &args.callee());
+
+    XPCCallContext ccx(cx, obj, nullptr, JSID_VOIDHANDLE, args.length(),
+                       args.array(), args.rval().address());
+    if (!ccx.IsValid())
+        return false;
+
+    PRE_HELPER_STUB
+    Call(wrapper, cx, obj, args, &retval);
+    POST_HELPER_STUB
+}
+
+bool
+XPC_WN_Helper_Construct(JSContext* cx, unsigned argc, Value* vp)
+{
+    JS::CallArgs args = JS::CallArgsFromVp(argc, vp);
+    RootedObject obj(cx, &args.callee());
+    if (!obj)
+        return false;
+
+    XPCCallContext ccx(cx, obj, nullptr, JSID_VOIDHANDLE, args.length(),
+                       args.array(), args.rval().address());
+    if (!ccx.IsValid())
+        return false;
+
+    PRE_HELPER_STUB
+    Construct(wrapper, cx, obj, args, &retval);
+    POST_HELPER_STUB
+}
+
+bool
+XPC_WN_Helper_HasInstance(JSContext* cx, HandleObject obj, MutableHandleValue valp, bool* bp)
+{
+    bool retval2;
+    PRE_HELPER_STUB
+    HasInstance(wrapper, cx, obj, valp, &retval2, &retval);
+    *bp = retval2;
+    POST_HELPER_STUB
+}
+
+void
+XPC_WN_Helper_Finalize(js::FreeOp* fop, JSObject* obj)
+{
+    WrappedNativeFinalize(fop, obj, WN_HELPER);
+}
+
+bool
+XPC_WN_Helper_Resolve(JSContext* cx, HandleObject obj, HandleId id, bool* resolvedp)
+{
+    nsresult rv = NS_OK;
+    bool retval = true;
+    bool resolved = false;
+    XPCCallContext ccx(cx, obj);
+    XPCWrappedNative* wrapper = ccx.GetWrapper();
+    THROW_AND_RETURN_IF_BAD_WRAPPER(cx, wrapper);
+
+    RootedId old(cx, ccx.SetResolveName(id));
+
+    XPCNativeScriptableInfo* si = wrapper->GetScriptableInfo();
+    if (si && si->GetFlags().WantResolve()) {
+        XPCWrappedNative* oldResolvingWrapper;
+        bool allowPropMods = si->GetFlags().AllowPropModsDuringResolve();
+
+        if (allowPropMods)
+            oldResolvingWrapper = ccx.SetResolvingWrapper(wrapper);
+
+        rv = si->GetCallback()->Resolve(wrapper, cx, obj, id, &resolved, &retval);
+
+        if (allowPropMods)
+            (void)ccx.SetResolvingWrapper(oldResolvingWrapper);
+    }
+
+    old = ccx.SetResolveName(old);
+    MOZ_ASSERT(old == id, "bad nest");
+
+    if (NS_FAILED(rv)) {
+        return Throw(rv, cx);
+    }
+
+    if (resolved) {
+        *resolvedp = true;
+    } else if (wrapper->HasMutatedSet()) {
+        // We are here if scriptable did not resolve this property and
+        // it *might* be in the instance set but not the proto set.
+
+        XPCNativeSet* set = wrapper->GetSet();
+        XPCNativeSet* protoSet = wrapper->HasProto() ?
+                                    wrapper->GetProto()->GetSet() : nullptr;
+        XPCNativeMember* member = nullptr;
+        RefPtr<XPCNativeInterface> iface;
+        bool IsLocal = false;
+
+        if (set->FindMember(id, &member, &iface, protoSet, &IsLocal) &&
+            IsLocal) {
+            XPCWrappedNative* oldResolvingWrapper;
+
+            XPCNativeScriptableFlags siFlags(0);
+            if (si)
+                siFlags = si->GetFlags();
+
+            XPCWrappedNative* wrapperForInterfaceNames =
+                siFlags.DontReflectInterfaceNames() ? nullptr : wrapper;
+
+            oldResolvingWrapper = ccx.SetResolvingWrapper(wrapper);
+            retval = DefinePropertyIfFound(ccx, obj, id,
+                                           set, iface, member,
+                                           wrapper->GetScope(),
+                                           false,
+                                           wrapperForInterfaceNames,
+                                           nullptr, si,
+                                           JSPROP_ENUMERATE, resolvedp);
+            (void)ccx.SetResolvingWrapper(oldResolvingWrapper);
+        }
+    }
+
+    return retval;
+}
+
+bool
+XPC_WN_Helper_Enumerate(JSContext* cx, HandleObject obj)
+{
+    XPCCallContext ccx(cx, obj);
+    XPCWrappedNative* wrapper = ccx.GetWrapper();
+    THROW_AND_RETURN_IF_BAD_WRAPPER(cx, wrapper);
+
+    XPCNativeScriptableInfo* si = wrapper->GetScriptableInfo();
+    if (!si || !si->GetFlags().WantEnumerate())
+        return Throw(NS_ERROR_XPC_BAD_OP_ON_WN_PROTO, cx);
+
+    if (!XPC_WN_Shared_Enumerate(cx, obj))
+        return false;
+
+    bool retval = true;
+    nsresult rv = si->GetCallback()->Enumerate(wrapper, cx, obj, &retval);
+    if (NS_FAILED(rv))
+        return Throw(rv, cx);
+    return retval;
+}
+
+/***************************************************************************/
+
+static bool
+XPC_WN_JSOp_Enumerate(JSContext* cx, HandleObject obj, AutoIdVector& properties,
+                      bool enumerableOnly)
+{
+    XPCCallContext ccx(cx, obj);
+    XPCWrappedNative* wrapper = ccx.GetWrapper();
+    THROW_AND_RETURN_IF_BAD_WRAPPER(cx, wrapper);
+
+    XPCNativeScriptableInfo* si = wrapper->GetScriptableInfo();
+    if (!si || !si->GetFlags().WantNewEnumerate())
+        return Throw(NS_ERROR_XPC_BAD_OP_ON_WN_PROTO, cx);
+
+    if (!XPC_WN_Shared_Enumerate(cx, obj))
+        return false;
+
+    bool retval = true;
+    nsresult rv = si->GetCallback()->NewEnumerate(wrapper, cx, obj, properties, &retval);
+    if (NS_FAILED(rv))
+        return Throw(rv, cx);
+    return retval;
+}
+
+/***************************************************************************/
+
+// static
+XPCNativeScriptableInfo*
+XPCNativeScriptableInfo::Construct(const XPCNativeScriptableCreateInfo* sci)
+{
+    MOZ_ASSERT(sci, "bad param");
+    nsCOMPtr<nsIXPCScriptable> callback = sci->GetCallback();
+    MOZ_ASSERT(callback);
+    MOZ_ASSERT(callback->GetScriptableFlags() == sci->GetFlags());
+    return new XPCNativeScriptableInfo(callback);
+}
+
+const js::ObjectOps XPC_WN_ObjectOpsWithEnumerate = {
+    nullptr,  // lookupProperty
+    nullptr,  // defineProperty
+    nullptr,  // hasProperty
+    nullptr,  // getProperty
+    nullptr,  // setProperty
+    nullptr,  // getOwnPropertyDescriptor
+    nullptr,  // deleteProperty
+    nullptr,  // watch
+    nullptr,  // unwatch
+    nullptr,  // getElements
+    XPC_WN_JSOp_Enumerate,
+    nullptr,  // funToString
+};
+
+/***************************************************************************/
+/***************************************************************************/
+
+// Compatibility hack.
+//
+// XPConnect used to do all sorts of funny tricks to find the "correct"
+// |this| object for a given method (often to the detriment of proper
+// call/apply). When these tricks were removed, a fair amount of chrome
+// code broke, because it was relying on being able to grab methods off
+// some XPCOM object (like the nsITelemetry service) and invoke them without
+// a proper |this|. So, if it's quite clear that we're in this situation and
+// about to use a |this| argument that just won't work, fix things up.
+//
+// This hack is only useful for getters/setters if someone sets an XPCOM object
+// as the prototype for a vanilla JS object and expects the XPCOM attributes to
+// work on the derived object, which we really don't want to support. But we
+// handle it anyway, for now, to minimize regression risk on an already-risky
+// landing.
+//
+// This hack is mainly useful for the NoHelper JSClass. We also fix up
+// Components.utils because it implements nsIXPCScriptable (giving it a custom
+// JSClass) but not nsIClassInfo (which would put the methods on a prototype).
+
+#define IS_NOHELPER_CLASS(clasp) (clasp == &XPC_WN_NoHelper_JSClass)
+#define IS_CU_CLASS(clasp) (clasp->name[0] == 'n' && !strcmp(clasp->name, "nsXPCComponents_Utils"))
+
+MOZ_ALWAYS_INLINE JSObject*
+FixUpThisIfBroken(JSObject* obj, JSObject* funobj)
+{
+    if (funobj) {
+        JSObject* parentObj =
+            &js::GetFunctionNativeReserved(funobj,
+                                           XPC_FUNCTION_PARENT_OBJECT_SLOT).toObject();
+        const js::Class* parentClass = js::GetObjectClass(parentObj);
+        if (MOZ_UNLIKELY((IS_NOHELPER_CLASS(parentClass) || IS_CU_CLASS(parentClass)) &&
+                         (js::GetObjectClass(obj) != parentClass)))
+        {
+            return parentObj;
+        }
+    }
+    return obj;
+}
+
+bool
+XPC_WN_CallMethod(JSContext* cx, unsigned argc, Value* vp)
+{
+    JS::CallArgs args = JS::CallArgsFromVp(argc, vp);
+    MOZ_ASSERT(JS_TypeOfValue(cx, args.calleev()) == JSTYPE_FUNCTION, "bad function");
+    RootedObject funobj(cx, &args.callee());
+
+    RootedObject obj(cx, JS_THIS_OBJECT(cx, vp));
+    if (!obj)
+        return false;
+
+    obj = FixUpThisIfBroken(obj, funobj);
+    XPCCallContext ccx(cx, obj, funobj, JSID_VOIDHANDLE, args.length(),
+                       args.array(), vp);
+    XPCWrappedNative* wrapper = ccx.GetWrapper();
+    THROW_AND_RETURN_IF_BAD_WRAPPER(cx, wrapper);
+
+    RefPtr<XPCNativeInterface> iface;
+    XPCNativeMember*    member;
+
+    if (!XPCNativeMember::GetCallInfo(funobj, &iface, &member))
+        return Throw(NS_ERROR_XPC_CANT_GET_METHOD_INFO, cx);
+    ccx.SetCallInfo(iface, member, false);
+    return XPCWrappedNative::CallMethod(ccx);
+}
+
+bool
+XPC_WN_GetterSetter(JSContext* cx, unsigned argc, Value* vp)
+{
+    JS::CallArgs args = JS::CallArgsFromVp(argc, vp);
+    MOZ_ASSERT(JS_TypeOfValue(cx, args.calleev()) == JSTYPE_FUNCTION, "bad function");
+    RootedObject funobj(cx, &args.callee());
+
+    RootedObject obj(cx, JS_THIS_OBJECT(cx, vp));
+    if (!obj)
+        return false;
+
+    obj = FixUpThisIfBroken(obj, funobj);
+    XPCCallContext ccx(cx, obj, funobj, JSID_VOIDHANDLE, args.length(),
+                       args.array(), vp);
+    XPCWrappedNative* wrapper = ccx.GetWrapper();
+    THROW_AND_RETURN_IF_BAD_WRAPPER(cx, wrapper);
+
+    RefPtr<XPCNativeInterface> iface;
+    XPCNativeMember*    member;
+
+    if (!XPCNativeMember::GetCallInfo(funobj, &iface, &member))
+        return Throw(NS_ERROR_XPC_CANT_GET_METHOD_INFO, cx);
+
+    if (args.length() != 0 && member->IsWritableAttribute()) {
+        ccx.SetCallInfo(iface, member, true);
+        bool retval = XPCWrappedNative::SetAttribute(ccx);
+        if (retval)
+            args.rval().set(args[0]);
+        return retval;
+    }
+    // else...
+
+    ccx.SetCallInfo(iface, member, false);
+    return XPCWrappedNative::GetAttribute(ccx);
+}
+
+/***************************************************************************/
+
+static bool
+XPC_WN_Shared_Proto_Enumerate(JSContext* cx, HandleObject obj)
+{
+    MOZ_ASSERT(js::GetObjectClass(obj) == &XPC_WN_ModsAllowed_Proto_JSClass ||
+               js::GetObjectClass(obj) == &XPC_WN_NoMods_Proto_JSClass,
+               "bad proto");
+    XPCWrappedNativeProto* self =
+        (XPCWrappedNativeProto*) xpc_GetJSPrivate(obj);
+    if (!self)
+        return false;
+
+    XPCNativeSet* set = self->GetSet();
+    if (!set)
+        return false;
+
+    XPCCallContext ccx(cx);
+    if (!ccx.IsValid())
+        return false;
+
+    uint16_t interface_count = set->GetInterfaceCount();
+    XPCNativeInterface** interfaceArray = set->GetInterfaceArray();
+    for (uint16_t i = 0; i < interface_count; i++) {
+        XPCNativeInterface* iface = interfaceArray[i];
+        uint16_t member_count = iface->GetMemberCount();
+
+        for (uint16_t k = 0; k < member_count; k++) {
+            if (!xpc_ForcePropertyResolve(cx, obj, iface->GetMemberAt(k)->GetName()))
+                return false;
+        }
+    }
+
+    return true;
+}
+
+static void
+XPC_WN_Shared_Proto_Finalize(js::FreeOp* fop, JSObject* obj)
+{
+    // This can be null if xpc shutdown has already happened
+    XPCWrappedNativeProto* p = (XPCWrappedNativeProto*) xpc_GetJSPrivate(obj);
+    if (p)
+        p->JSProtoObjectFinalized(fop, obj);
+}
+
+static void
+XPC_WN_Shared_Proto_ObjectMoved(JSObject* obj, const JSObject* old)
+{
+    // This can be null if xpc shutdown has already happened
+    XPCWrappedNativeProto* p = (XPCWrappedNativeProto*) xpc_GetJSPrivate(obj);
+    if (p)
+        p->JSProtoObjectMoved(obj, old);
+}
+
+static void
+XPC_WN_Shared_Proto_Trace(JSTracer* trc, JSObject* obj)
+{
+    // This can be null if xpc shutdown has already happened
+    XPCWrappedNativeProto* p =
+        (XPCWrappedNativeProto*) xpc_GetJSPrivate(obj);
+    if (p)
+        p->TraceInside(trc);
+}
+
+/*****************************************************/
+
+static bool
+XPC_WN_ModsAllowed_Proto_Resolve(JSContext* cx, HandleObject obj, HandleId id, bool* resolvep)
+{
+    MOZ_ASSERT(js::GetObjectClass(obj) == &XPC_WN_ModsAllowed_Proto_JSClass,
+               "bad proto");
+
+    XPCWrappedNativeProto* self =
+        (XPCWrappedNativeProto*) xpc_GetJSPrivate(obj);
+    if (!self)
+        return false;
+
+    XPCCallContext ccx(cx);
+    if (!ccx.IsValid())
+        return false;
+
+    XPCNativeScriptableInfo* si = self->GetScriptableInfo();
+    return DefinePropertyIfFound(ccx, obj, id,
+                                 self->GetSet(), nullptr, nullptr,
+                                 self->GetScope(),
+                                 true, nullptr, nullptr, si,
+                                 JSPROP_ENUMERATE, resolvep);
+}
+
+static const js::ClassOps XPC_WN_ModsAllowed_Proto_JSClassOps = {
+    nullptr,                            // addProperty
+    nullptr,                            // delProperty
+    nullptr,                            // getProperty
+    nullptr,                            // setProperty
+    XPC_WN_Shared_Proto_Enumerate,      // enumerate
+    XPC_WN_ModsAllowed_Proto_Resolve,   // resolve
+    nullptr,                            // mayResolve
+    XPC_WN_Shared_Proto_Finalize,       // finalize
+    nullptr,                            // call
+    nullptr,                            // construct
+    nullptr,                            // hasInstance
+    XPC_WN_Shared_Proto_Trace,          // trace
+};
+
+static const js::ClassExtension XPC_WN_Shared_Proto_ClassExtension = {
+    nullptr,    /* weakmapKeyDelegateOp */
+    XPC_WN_Shared_Proto_ObjectMoved
+};
+
+const js::Class XPC_WN_ModsAllowed_Proto_JSClass = {
+    "XPC_WN_ModsAllowed_Proto_JSClass",
+    XPC_WRAPPER_FLAGS,
+    &XPC_WN_ModsAllowed_Proto_JSClassOps,
+    JS_NULL_CLASS_SPEC,
+    &XPC_WN_Shared_Proto_ClassExtension,
+    JS_NULL_OBJECT_OPS
+};
+
+/***************************************************************************/
+
+static bool
+XPC_WN_OnlyIWrite_Proto_AddPropertyStub(JSContext* cx, HandleObject obj, HandleId id,
+                                        HandleValue v)
+{
+    MOZ_ASSERT(js::GetObjectClass(obj) == &XPC_WN_NoMods_Proto_JSClass,
+               "bad proto");
+
+    XPCWrappedNativeProto* self =
+        (XPCWrappedNativeProto*) xpc_GetJSPrivate(obj);
+    if (!self)
+        return false;
+
+    XPCCallContext ccx(cx);
+    if (!ccx.IsValid())
+        return false;
+
+    // Allow XPConnect to add the property only
+    if (ccx.GetResolveName() == id)
+        return true;
+
+    return Throw(NS_ERROR_XPC_BAD_OP_ON_WN_PROTO, cx);
+}
+
+static bool
+XPC_WN_NoMods_Proto_Resolve(JSContext* cx, HandleObject obj, HandleId id, bool* resolvedp)
+{
+    MOZ_ASSERT(js::GetObjectClass(obj) == &XPC_WN_NoMods_Proto_JSClass,
+               "bad proto");
+
+    XPCWrappedNativeProto* self =
+        (XPCWrappedNativeProto*) xpc_GetJSPrivate(obj);
+    if (!self)
+        return false;
+
+    XPCCallContext ccx(cx);
+    if (!ccx.IsValid())
+        return false;
+
+    XPCNativeScriptableInfo* si = self->GetScriptableInfo();
+
+    return DefinePropertyIfFound(ccx, obj, id,
+                                 self->GetSet(), nullptr, nullptr,
+                                 self->GetScope(),
+                                 true, nullptr, nullptr, si,
+                                 JSPROP_READONLY |
+                                 JSPROP_PERMANENT |
+                                 JSPROP_ENUMERATE, resolvedp);
+}
+
+static const js::ClassOps XPC_WN_NoMods_Proto_JSClassOps = {
+    XPC_WN_OnlyIWrite_Proto_AddPropertyStub,   // addProperty
+    XPC_WN_CantDeletePropertyStub,             // delProperty
+    nullptr,                                   // getProperty
+    nullptr,                                   // setProperty
+    XPC_WN_Shared_Proto_Enumerate,             // enumerate
+    XPC_WN_NoMods_Proto_Resolve,               // resolve
+    nullptr,                                   // mayResolve
+    XPC_WN_Shared_Proto_Finalize,              // finalize
+    nullptr,                                   // call
+    nullptr,                                   // construct
+    nullptr,                                   // hasInstance
+    XPC_WN_Shared_Proto_Trace,                 // trace
+};
+
+const js::Class XPC_WN_NoMods_Proto_JSClass = {
+    "XPC_WN_NoMods_Proto_JSClass",
+    XPC_WRAPPER_FLAGS,
+    &XPC_WN_NoMods_Proto_JSClassOps,
+    JS_NULL_CLASS_SPEC,
+    &XPC_WN_Shared_Proto_ClassExtension,
+    JS_NULL_OBJECT_OPS
+};
+
+/***************************************************************************/
+
+static bool
+XPC_WN_TearOff_Enumerate(JSContext* cx, HandleObject obj)
+{
+    XPCCallContext ccx(cx, obj);
+    XPCWrappedNative* wrapper = ccx.GetWrapper();
+    THROW_AND_RETURN_IF_BAD_WRAPPER(cx, wrapper);
+
+    XPCWrappedNativeTearOff* to = ccx.GetTearOff();
+    XPCNativeInterface* iface;
+
+    if (!to || nullptr == (iface = to->GetInterface()))
+        return Throw(NS_ERROR_XPC_BAD_OP_ON_WN_PROTO, cx);
+
+    uint16_t member_count = iface->GetMemberCount();
+    for (uint16_t k = 0; k < member_count; k++) {
+        if (!xpc_ForcePropertyResolve(cx, obj, iface->GetMemberAt(k)->GetName()))
+            return false;
+    }
+
+    return true;
+}
+
+static bool
+XPC_WN_TearOff_Resolve(JSContext* cx, HandleObject obj, HandleId id, bool* resolvedp)
+{
+    XPCCallContext ccx(cx, obj);
+    XPCWrappedNative* wrapper = ccx.GetWrapper();
+    THROW_AND_RETURN_IF_BAD_WRAPPER(cx, wrapper);
+
+    XPCWrappedNativeTearOff* to = ccx.GetTearOff();
+    XPCNativeInterface* iface;
+
+    if (!to || nullptr == (iface = to->GetInterface()))
+        return Throw(NS_ERROR_XPC_BAD_OP_ON_WN_PROTO, cx);
+
+    return DefinePropertyIfFound(ccx, obj, id, nullptr, iface, nullptr,
+                                 wrapper->GetScope(),
+                                 true, nullptr, nullptr, nullptr,
+                                 JSPROP_READONLY |
+                                 JSPROP_PERMANENT |
+                                 JSPROP_ENUMERATE, resolvedp);
+}
+
+static void
+XPC_WN_TearOff_Finalize(js::FreeOp* fop, JSObject* obj)
+{
+    XPCWrappedNativeTearOff* p = (XPCWrappedNativeTearOff*)
+        xpc_GetJSPrivate(obj);
+    if (!p)
+        return;
+    p->JSObjectFinalized();
+}
+
+static void
+XPC_WN_TearOff_ObjectMoved(JSObject* obj, const JSObject* old)
+{
+    XPCWrappedNativeTearOff* p = (XPCWrappedNativeTearOff*)
+        xpc_GetJSPrivate(obj);
+    if (!p)
+        return;
+    p->JSObjectMoved(obj, old);
+}
+
+// Make sure XPC_WRAPPER_FLAGS has no reserved slots, so our
+// XPC_WN_TEAROFF_RESERVED_SLOTS value is OK.
+
+static_assert(((XPC_WRAPPER_FLAGS >> JSCLASS_RESERVED_SLOTS_SHIFT) &
+               JSCLASS_RESERVED_SLOTS_MASK) == 0,
+              "XPC_WRAPPER_FLAGS should not include any reserved slots");
+
+static const js::ClassOps XPC_WN_Tearoff_JSClassOps = {
+    XPC_WN_OnlyIWrite_AddPropertyStub,  // addProperty
+    XPC_WN_CantDeletePropertyStub,      // delProperty
+    nullptr,                            // getProperty
+    nullptr,                            // setProperty
+    XPC_WN_TearOff_Enumerate,           // enumerate
+    XPC_WN_TearOff_Resolve,             // resolve
+    nullptr,                            // mayResolve
+    XPC_WN_TearOff_Finalize,            // finalize
+    nullptr,                            // call
+    nullptr,                            // construct
+    nullptr,                            // hasInstance
+    nullptr,                            // trace
+};
+
+static const js::ClassExtension XPC_WN_Tearoff_JSClassExtension = {
+    nullptr,                            // weakmapKeyDelegateOp
+    XPC_WN_TearOff_ObjectMoved
+};
+
+const js::Class XPC_WN_Tearoff_JSClass = {
+    "WrappedNative_TearOff",
+    XPC_WRAPPER_FLAGS |
+    JSCLASS_HAS_RESERVED_SLOTS(XPC_WN_TEAROFF_RESERVED_SLOTS),
+    &XPC_WN_Tearoff_JSClassOps,
+    JS_NULL_CLASS_SPEC,
+    &XPC_WN_Tearoff_JSClassExtension
+};