init: Add Uptime.DBusCrash histogram.

Add a metric to record the system's uptime when it is
rebooted automatically after a dbus-daemon crash.

BUG=chromium:432980
TEST=manual: forced a crash and then checked that metric was
     reported to chrome after reboot

Change-Id: I58d37b905fc0dd4f15961eae22859a7e67e9ae08
Reviewed-on: https://chromium-review.googlesource.com/239262
Trybot-Ready: Dan Erat <derat@chromium.org>
Reviewed-by: David Zeuthen <zeuthen@chromium.org>
Commit-Queue: Dan Erat <derat@chromium.org>
Tested-by: Dan Erat <derat@chromium.org>
1 file changed