D8474: Reserve size in container

[Laurent Montel]

mlaurent added a reviewer: hein.

REPOSITORY
  R119 Plasma Desktop

REVISION DETAIL
  https://phabricator.kde.org/D8474

To: mlaurent, hein
Cc: plasma-devel, ZrenBot, progwolff, lesliezhai, ali-mohamed, jensreuterberg, 
abetts, sebas, apol, mart