We will soon replace regular menu items in the calendar drop-down
with more complex elements.
However there will still be items that should close the drop down
when activated - rather than making the menu available throughout
the hierarchy (and eventually from outside as well when we add the
notifications list), have a public method on a global object just
like the ubiquitous Main.overview.hide().
https://bugzilla.gnome.org/show_bug.cgi?id=744817
f84addcadc