In the latest Ubuntu 14.04 old systray was replaced with app indicator, so the systray-whitelist doesn't exist anymore.
Anyone knows how to show gmusicbrowser in new app indicator?
There is still a work-around : installing a modified version of unity from this ppa : https://launchpad.net/~gurqn/+archive/systray-trusty (found in this forum thread (http://ubuntuforums.org/showthread.php?t=2217458))
But for those that really want to use this new app indicator, I'm going to implement it, it shouldn't be too hard, though of course its functionality will be very limited. I plan to let the user choose between the different types of indicators (gnome 3 has its own IIRC)
See also this bug I've just replied to : https://github.com/squentin/gmusicbrowser/issues/82
same problem here with Gnome 3.12.2
I've just committed a basic app indicator plugin. (requires libgtk2-appindicator-perl)
I plan to reorganize the trayicon/indicator/notify system in a single place that will let you choose among the different alternatives, and add a desktop-agnostic alternative that, for example, will let you pop-up the menu/traytip window from a hot-spot (such as a corner).
About gnome shell, you have to add an extension, such as TopIcons, to make the icon appear. Note that, at least with this extension (I don't know if there are others), the traytip window doesn't pop-up on mouse hover :(