There is only one call site, so I believe it's best to have the marker type there.
I think it's cleaner this way, this marker type doesn't need to be present in a header shared by all users of the profiler.
The only downside is that we cannot unit-test this particular marker type automatically anymore, but I don't think it's strictly needed:
- There are still plenty of tests checking that generic marker types work end-to-end, so we can have some confidence this specific one can do its job.
- If it somehow started to fail, either it would be quickly found that it breaks the front-end, or it wouldn't have any visible effect in which case it's not a big issue.
Follow-up bug 1665810 will instead add a higher-level xpcshell test or mochitest.
Differential Revision: https://phabricator.services.mozilla.com/D90185
a811180396