A test page that users can load (from anywhere in the world).
It renders a fairly common example page while explicitly measuring and reporting both network and browser performance to be reported back to WMF.
(and perhaps loads it a second time to measure cache effects)
The idea being that when anyone anywhere is having performance problems loading wikipedia, that they can go to this page and have it perform some diagnostics and optionally share those results with people who are interested in improving performance, etc.
Apologies if this has already been implemented/proposed.
I bring it up because I have been asked to create a simulation environment to emulate 'poor network performance' and I had trouble coming up with a baseline.
I realize that there's some prior art in the network latency space here.