Summary:
Deleted has lifetime bounded to effects and scene.
We can't discard Deleted before EffectsHandler is destroyed because
effects that referenced it may call unrefWindow.
On the other hand, the fact that Deleted may outlive scene doesn't
make sense because Deleted exist purely for animation purposes and
nothing more.
This change arranges lifetime of Deleted so it's more reasonable.
Reviewers: #kwin, davidedmundson
Reviewed By: #kwin, davidedmundson
Subscribers: graesslin, kwin
Tags: #kwin
Differential Revision: https://phabricator.kde.org/D18914
10fdf2a220