Change effective on 12 April 2016
Restart events are now available as a beta feature in the Metrics Events table for Common Runtime users. A restart event indicates that for your app, one or more dynos of a given type were restarted during that time interval. Multiple restarts will show up as one event for each 1 or 10 minute interval (depending on your selected resolution). More information on restart event types is available on the Application Metrics Beta Channel page.