popup: fix resize issue when action area and title area is absent.
popup: fix resize issue when action area and title area is absent.

Summary:
set scroller size in content_set.

Resolves: T2623
@fix

Test Plan:
1. run ecrire
2. Add some text in newfile
3. Close ecrire
4. a almost zero size popup.

Reviewers: tasn, herdsman, raster, SanghyeonLee, stefan_schmidt

Reviewed By: stefan_schmidt

Subscribers: stefan_schmidt, herb, seoz

Maniphest Tasks: T2623

Differential Revision: https://phab.enlightenment.org/D2901

tasn/elementary,rvandegrift/elementary,rvandegrift/elementary,rvandegrift/elementary,tasn/elementary,tasn/elementary,tasn/elementary,rvandegrift/elementary,tasn/elementary