### Problem to solve Currently the performance testing is checking times available through the Timings API:  We might want to track also moments after DOMready and even after `window.onload`. We should find a way to track this globally on several pages but do it in a generic way, to not have to update the performance tests every time we have a new app We can focus this effort on the MR page example but keep a generic approach. ### Intended users Developers that develop and make use of the performance automated testing. ### Further details Context: https://gitlab.com/groups/gitlab-org/-/epics/805 ### Proposal Thinking of having a generic custom event that multiple Vue apps can use to record the moment the full app is setup in a global object so that the performance test script can check that like it does for the timing API. Question: is one event enough? Should we track several moments and have the performance tool calculate deltas between them? Or leave that for a later improvement? ### What does success look like, and how can we measure that? Able to identify when an MR worsens the overall perceived performance or Time to Interaction with a full-fledged Vue app. ### Links / references