How to let qtwebengine use system locale language and load correct .pak file?

I use zh_CN, I want my qtwebengine use chinese as default ui, but I don't know how to achieve this.

For example, in chrome, alert() shows like:

but in qtwebengineview, it shows like

and, chrome show like:

but qtwebengine shows like:

Every ui in qtwebengine seems to use english as default, but when i try to print my view->locale(), it shows: QLocale(Chinese, Default, China), and although I delete everything in qtwebengine_locales, this does not seem to have any effect.

So, how to let qtwebengine load zh-CN.pak correctly?