Cannot focus on TextInput in SkinnablePopupContainer

Steps to reproduce:
1. Add a SkinnablePopupContainer
2. Add a TextInput
3. Try to set focus to the TextInput

Actual Results:
No focus, no soft keyboard

Expected Results:
Focus on TextInput, soft keyboard popup

Workaround (if any):
Listen to SkinnablePopUpContainers open event instead of the TextInput's addedToStage. The focusManager is not assigned for the pop-up when the TextInput is added to the stage.

Also tried with PopupManager.addPopUp(...), same result.

It seems like no focusManager is being inserted despite the fact that SkinnablePopupContainer implements IFocusManagerContainer.

Attached: test project