GitLab

This CL converts the SessionLengthLimiter from a RepeatingTimer that
fires once per second to a OneShotTimer that fires when the session
time is up and the user should be logged out.

BUG=175797
TEST=Manual, unittests


Review URL: https://chromiumcodereview.appspot.com/12218123

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@182214 0039d316-1c4b-4281-b951-d872f2087c98