This isn’t something that the tracker currently handles itself currently. We’re interested in the concept and are at very early stages of exploring something along these lines - but even if we have promising results from those experiments it would still likely be a while before it would get scheduled into our roadmap and delivered.
It is possible, however, to handle the logic of measuring this data yourself, and track the results using a custom event or context. The most striaghtforward way to do so would be to instrument something like the Paint Timing API outside the tracker, define custom schemas, and track the data against those schemas.
If this is something you do embark on, it would be awesome to hear back from you on how you instrumented it and what the results are - oftentimes, if we’re considering how feasible a feature is, then having someone show us a viable proof of concept will lend weight to the idea and accelerate the discovery phase - especially if it’s been instrumented in a production environment and we can learn from the results.
Hope that’s helpful!