Restore the "Ask me" behavior on power button press

[Cosimo Cecchi <cosimoc gnome org>]

Hi everyone,

This is both a hard code freeze break request and a RFC.

The current gnome-control-center Power panel has an "Ask me" option for
button press. That option used to bring up gnome-session's power off
dialog, but right now it doesn't do anything.
I digged through the git log of gnome-settings-daemon and
gnome-power-manager and it seems that the code to implement that
behavior got removed on purpose due to bug [1], but the option was left
untouched in the panel combobox.
Bugzilla has been down for a while today, so I can't see the rationale
of the removal in the bug report, but the matter of fact is that we have
a broken option for the highly-controversial power-off-vs-suspend
feature.

I think we need to make a choice between removing the option entirely in
the control center panel, or re-wire the g-s-d and g-p-m code back in to
support the feature. I personally strongly prefer the second option
here; I talked with Jon McCann earlier today and he agrees with me too.

So, I prepared a patchset that just does that; you can find it here [2];
ideally, I would like to see this change go in for tomorrow's release
candidate. Thoughts?

[1] https://bugzilla.gnome.org/show_bug.cgi?id=643976
[2] http://people.gnome.org/~cosimoc/fix-power/

Thanks,

Cosimo