Comment 4 for bug 1437510

As I understand it, dim-timeout is expected to be relative to activity-timeout. I have a branch for ubuntu-system-settings that changes dim-timeout whenever the activity-timeout gsetting value changes. This feels like a work around for broken logic. If we don't want to set dim-timeout separately, and remain relative to activity-timeout, we should drop the setting completely and ubuntu-system-compositor should dim the screen on activity-timeout - 10.