In order to clarify what the actual trigger for sending a ping is, it was suggested to add to the metrics ping documentation something that describes the onStop() event that we are using to make it clear what triggers this lifecycle event.

For example:
When your activity is no longer visible to the user, it has entered the Stopped state, and the system invokes the onStop() callback. This may occur, for example, when a newly launched activity covers the entire screen. The system may also call onStop() when the activity has finished running, and is about to be terminated.

We could additionally use this bug to add a minimal documentation about the rationale for each ping. What's the difference between baseline, metrics and events ping?