Indicates whether the "max length" countdown dialog is open to warn the user of an impending session end.
Data is the number of seconds remaining until session end, or null if the countdown dialog is not open.
also module-common-session/lib/common/actions.sessionMaxLengthTimerCountdown module-common-session/lib/common/actions.sessionMaxLengthRenew
Indicates whether the "max length" countdown dialog is open to warn the user of an impending session end.