NotShowIn and OnlyShowIn in .desktop files are ignored

Applications with .desktop file containing NotShowIn=Unity or OnlyShowIn=/!Unity/ should be treated as Hidden. This affects libertine, as some applications with these properties are currently shown resulting in unlaunchable applications (#1606593). There are certainly many more libertine applications which will be affected by this and cause the users to see unlaunchable apps.

This bug can be traced directly to the workaround in the Desktop constructor in application-info-desktop.c, lines 185,186 at time of writing. A temporary workaround is causing the launcher to work unexpectedly. This seems to be an issue that has permeated from deeper within the system, so this bug is being filed to continue the linkage to the source of the issue.

I discussed with @ted why this has yet to be undone and have included the chat log:

<ted> larryprice: So the issue is that design doesn't want the media player to show up in the list of applications.
<ted> larryprice: But they do want users to be able to play media files and have them show up.
<ted> larryprice: The proper way to do that is to have a trusted prompt overlay that plays the video.
<ted> larryprice: But... the trusted prompt overlays basically allow you to take over the application, and you can't remove them.
<ted> larryprice: So if something like the media player (or something else) was to hang or crash you'd lose access to your app.
<ted> larryprice: Thus we need some way for Unity8 to allow closing the trusted prompt overlay.
<ted> larryprice: In the mean time, we're making media player an app, but just marking its desktop files incorrectly to cause the application grid to invalidate it.
<ted> larryprice: Since UAL didn't check that before when launching, it worked, and we've become dependent on that working.
<larryprice> ted, geez louise
<ted> In general, the U8 team has said they will fix this, but eh, it's been a while that I've pinged them on it. I don't think they've fixed it yet.