Change demo mode derelict detection.
This CL changes the demo mode derelict detection to now take the total time on OOBE instead of idle time on OOBE. This is a much more accurate representation of a derelict state than idle time since a machine can be not idle for 8 hours at a stretch and still be effectively derelict if it is still sitting at OOBE after 8 hours.

R=xiyuan@chromium.org
BUG=345436
TEST=Use the --oobe-timer-interval flag to test the new functionality and verify it works correctly.

Review URL: https://codereview.chromium.org/184033002

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@254267 0039d316-1c4b-4281-b951-d872f2087c98
SVN changes up to revision 254267