D8524: Add a signal notifying a change in the names of running activities.

[Eike Hein]

hein added a dependent revision: D8525: Refresh when the names of the running 
activities change..

REPOSITORY
  R120 Plasma Workspace

REVISION DETAIL
  https://phabricator.kde.org/D8524

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