Comment 8 for bug 740754

Hm, no, gdm is supposed to know both LANG and LANGUAGE, the upstart job explicitly sources /etc/default/locale before launching gdm-binary:

    if [ -r /etc/default/locale ]; then
        . /etc/default/locale
        export LANG LANGUAGE
    elif [ -r /etc/environment ]; then
        . /etc/environment
        export LANG LANGUAGE
    fi
    export XORGCONFIG

    exec gdm-binary $CONFIG_FILE

and this also seems to work here:

$ sudo cat /proc/`pidof gdm-binary`/environ | xargs -0n1 | grep ^LANG
LANGUAGE=de:en
LANG=de_DE.UTF-8

$ sudo cat /proc/`pidof gdm-session-worker`/environ | xargs -0n1 | grep ^LANG
LANG=de_DE.UTF-8
LANGUAGE=de:en