Maybe the bug is related to ligthdm / upstart rather to xorg, refering to comment in bug report https://bugs.launchpad.net/ubuntu/+source/lightdm/+bug/799069
Maybe the bug is related to ligthdm / upstart rather to xorg, refering to comment in bug report https:/ /bugs.launchpad .net/ubuntu/ +source/ lightdm/ +bug/799069