Bug 1256688 - Continue using getPropertyDescriptor for has in Sandbox. r=peterv

js/xpconnect/src/Sandbox.cpp

@@ -804,7 +804,14 @@ bool
 xpc::SandboxProxyHandler::has(JSContext* cx, JS::Handle<JSObject*> proxy,
                               JS::Handle<jsid> id, bool* bp) const
 {
-    return BaseProxyHandler::has(cx, proxy, id, bp);
+    // This uses getPropertyDescriptor for backward compatibility with
+    // the old BaseProxyHandler::has implementation.
+    Rooted<PropertyDescriptor> desc(cx);
+    if (!getPropertyDescriptor(cx, proxy, id, &desc))
+        return false;
+
+    *bp = !!desc.object();
+    return true;
 }
 bool
 xpc::SandboxProxyHandler::hasOwn(JSContext* cx, JS::Handle<JSObject*> proxy,