The new check I'm adding in bug 1828013 at the end of every browser chrome mochitests makes this leftover repeating timer visible when running the browser_WebrtcGlobalInformation.js test which creates peer connections in the parent process.

From looking at the code, it seems this timer is created in PeerConnectionCtx::Initialize, called by PeerConnectionCtx::InitializeGlobal which creates a PeerConnectionCtx instance stored in the global gInstance variable, which is only cleared by PeerConnectionCtx::Destroy, which is only called when receiving the "xpcom-will-shutdown" observer notification.

Could this timer instead be canceled when the last peer connection of the process is closed?

EverySecondTelemetryCallback_m was already causing a performance issue in bug 1724417. At the time I didn't understand that the timer kept firing even after all peer connections were closed.

The reason I'm filing this bug today is that it blocks landing of bug 1828013 (well, if there's no quick fix I'll find a way to add an exception for this timer, but it's unfortunate).

I think it would be possible to stop/resume when all PCs are gone. It might even clear up some intermittent failures on try.

Try looks fine.

https://treeherder.mozilla.org/jobs?repo=try&revision=98d5ef55c0bb4c7c000751c9a6fddd330d4917ae
https://treeherder.mozilla.org/jobs?repo=try&revision=51ed23213a5c1ff57bf7098f0ebe0f355eb89390

https://hg.mozilla.org/mozilla-central/rev/8d3cb7fb59ff