…e or a resume (#1607)
Count the relaunch grace period from when the deadline arrives, rather than from process start, so a long- running browser gives the user time to save their work. Reset the grace period on every resume to prevent an immediate restart after sleep; Gecko does not report how long the machine slept. Recheck the deadline when session restore completes so a deferred restart respects any extension caused by a resume or a later poll.
