What is TargetEnvironment=Unity?

I have a pure Lubuntu 12.10 installation. While looking at some .desktop files in /usr/share/applications I see TargetEnvironment=Unity.
One example is in the .desktop file for Google Chrome:

[NewWindow Shortcut Group]
Name=New Window
Exec=/opt/google/chrome/google-chrome
TargetEnvironment=Unity

[NewIncognito Shortcut Group]
Name=New Incognito Window
Exec=/opt/google/chrome/google-chrome --incognito
TargetEnvironment=Unity

Another example is the .desktop file for Inkscape:

[Drawing Shortcut Group]
Name=New Drawing
Exec=inkscape
TargetEnvironment=Unity

To find out what that means, I looked at Desktop Entry Specification - freedesktop.org standards and at UnityLaunchersAndDesktopFiles. But neither mentions TargetEnvironment. Hence my question.

TargetEnvironment makes the Shortcut Group (i.e. quicklist item) open only in Unity environments. You could also use the OnlyShowIn=Unity keyword.

Here's an old Launcher tutorial that mentions it.

As of here TargetEnvironment is deprecated.