D10487: Fix tray icon size scaling when changing the panel size (fix bug 360333)

[Piotr Kosinski]

pgkos edited the test plan for this revision.

REPOSITORY
  R120 Plasma Workspace

REVISION DETAIL
  https://phabricator.kde.org/D10487

To: pgkos, #plasma_workspaces
Cc: ngraham, davidedmundson, plasma-devel, ZrenBot, progwolff, lesliezhai, 
ali-mohamed, jensreuterberg, abetts, sebas, apol, mart