QWebEnginePage contextmenu internalization - how?

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Hello,
How to make display context menu of QWebEnginePage with local language? (e.g. polish)

I found in sources of Qt5.7.0 instalation:
C:\Qt\Qt5.7.0\5.7\msvc2013_64\translations\qtwebengine_locales*.pak files
Is this for make translation for menus, context menus?
How use it for QWebEnginePage?
By default it appears in english, even after instalation translator globally for my app.

Thank you for yours replays.
Best regards.