Code review comment for lp:~azzar1/unity/fix-994163

16 + typedef glib::Signal<void, GVolume*> VolumeSignal;
17 + sig_manager_.Add(new VolumeSignal(volume_, "changed", sigc::mem_fun(this, &DeviceLauncherIcon::OnVolumeChanged)));

Since DeviceLauncherIcon just uses one signal I think that you can avoid to use the SignalManager and save some overhead by just adding a glib::Signal class member and using its Connect method...