[Mirroring] centerPopUp() doesn't position window correctly with layoutDirection=='rtl'

Steps to reproduce:
1. Add layoutDirection=='rtl' to your Application. Place a custom component inside your application.
2. Open any popup from that component (Alert, for example) and make this component popup's parent
3. Call PopUpManager.centerPopUp() for this popup. (Alert does it automatically)

Actual Results:
PopUp appears in an odd place, and can even appear outside of a visible stage area

Expected Results:
PopUp should be centered inside component

Workaround (if any):