Use Performance API to add "User Timings"

[Turbo87]

I had implemented a similar thing using the on() event handlers for one of our projects and it was invaluable in tracking down slowness in our test suite. Having this implemented in QUnit by default makes it even more accessible for people that don't know about this API yet. :)

/cc @trentmwillis

[rwjblue]

I like it!

[trentmwillis]

Haven't done a full review, but I like this idea! A couple thoughts:

1. Looks like the Performance API has started to land in newer Node versions. It would be good if we supported that use case as well. Any issues with adding support for that?

2. Do you have any thoughts on adding tests for these? On the one hand, any tests are likely to feel like they're testing implementation details, but if users start querying the Performance marks/measurements, then we want to make sure we don't break them.

[Turbo87]

Yeah, looks like node could also be supported, but I'd rather land this first and add node support in a subsequent PR. Tests would be nice, but we'd have to mock the performance API, and I'm not sure if it's worth it 🤔

[Turbo87]

@trentmwillis I have a hard time finding any tests for the reports classes that I could extend. Did I miss anything? Do they exist?

[Turbo87]

@trentmwillis friendly reminder :)

[gabrielcsapo]

@trentmwillis bump

[trentmwillis]

Sorry y'all, I've been busy. I'll take a look at this sometime this week. Adding a reminder so I don't forget...

[trentmwillis]

The reports are tested indirectly via the "events" tests.

After reviewing again, I'm fine with landing this as-is. We can add Node support and tests in follow-up PRs.

Thanks! And sorry for taking so long to merge

[Turbo87]

awesome, thank you @trentmwillis :)

[Turbo87]

@trentmwillis any plans on a release in the near future?

[trentmwillis]

@Turbo87 yep, within the next day. See #1311 (comment)

[Turbo87]

Great, thanks a lot!

[stefanpenner]

awesome!