We could count how often documents have mutation event listeners. If they are being used a lot, it may take some more time to get rid of mutation events.
So the outcome would be something like y of x created documents had mutation event listeners.
Created attachment 566788 [details] [diff] [review] patch So I want to count how many (inner) windows have had mutation event listeners and how many hasn't had. Based on what about:telemetry reports, this does that.
Created attachment 566812 [details] [diff] [review] patch Just a bit nicer coding style.
Can we please also let devs know that mutation events will get deprecated at some point? Even if we don't have a replacement for them yet, more information seems better than less. We can even provide an eta of when replacement will be available.
Sure, but that has nothing to do with this bug :)
This is performance and usage-related, so fine privacy-wise. Clearing the flag.