Fix PopupMenuTest

Recent refactoring changed the internal implementation details
of the class name of the container that is used to show the
popup content.

Also in one of the tests (anchoring alignment) we no longer need
to account for the cumulative ancestor padding.

Bug: 27363875
Change-Id: Ia9c00a04f712e0279d296c22a49275fa9abd8815
1 file changed