Tests for PopupWindow public API change

Added tests for newly unhidden methods for PopupWindow, introduced in CL
I7fb4d8e28f0de889e110b7b90f71ebec9ab4cc9d.

Bug: 123769516
Bug: 123768511
Bug: 123768510
Bug: 123768589
Test: All widgets tests including new passed
Change-Id: I468b592a3ba2e5f2f895210d21843d328a454794
1 file changed