==== Background
Following on from {T296415}, we'd like to know how many users see the terms of use agreement infobox treatment and bounce from it.
==== Open Questions
1. Do we want to know how many //unique// users see the terms of use agreement? If so, then we need to log a unique value per user. However, we must avoid logging the user ID whenever possible. Could we salt and hash the user's ID? Would there be any privacy and/or security implications in sending a salted and hashed user ID to the client?
==== AC
[] When I sees the terms of use agreement infobox treatment, an event should be logged
** The `event_action` property should be `"init_disclaimer"`
[] When I have seen the terms of use agreement infobox treatment and I close the browser tab/window, an event should be logged
** The `event_action` property should be `"close_disclaimer"`
==== Notes
1. At the time of writing, the user will only see the terms of use agreement infobox treatment when:
** They have enabled IP Info via Special:Preferences; and
** They navigate to /wiki/Special:Contributions/$ip
1. For performance reasons, listen for [[ https://developer.mozilla.org/en-US/docs/Web/API/Window/beforeunload_event | the beforeunload event ]] (not the `unload` event)