animateIn and animateOut should not reset the scale, otherwise
extra animate calls (which are possible because the diff algorithm
in _redisplay is not optimal) cause unneeded movement.
Therefore, create new items hidden, and have the creator call
animateIn or set the scale/opacity properties manually.
adjustIconSize must be changed to always set the icon size temporarily,
otherwise the first time it computes the icon size with 0 scale.
https://bugzilla.gnome.org/show_bug.cgi?id=690643
