Dedupe calls to performance.measure

[ryanhamley]

Launch Checklist

• briefly describe the changes in this PR
  • This fixes Setting map option collectResourceTiming to true results in console errors #10303
  • I believe the error was always possible to hit but used to be very rare. With the introduction of two-phased tile loading in v2.0.0, the problem became much more prominent. Two-phased tile loading leads to two calls to loadTile and ultimately to perf.finish(). On the first call to perf.finish(), the entries for this._marks.start are cleared from the performance entry buffer. On the second call to perf.finish(), performance.measure() tries to use this._marks.start as the start mark but can't find entries in the performance buffer and throws an error.
  • This PR removes the fallback performance measurements because the Performance API is now supported in all GL JS supported browsers. It also moves the performance measurement for vector tiles into the DedupedRequest class so that the measurement isn't dependent on this.scheduler for timing.
• manually test the debug page
• apply changelog label ('bug', 'feature', 'docs', etc) or use the label 'skip changelog'
• add an entry inside this element for inclusion in the mapbox-gl-js changelog: <changelog>Prevent collectResourceTiming from causing errors when loading vector tiles</changelog>

[ansis]

I'm seeing a different problem that was introduced in v2.0.0.

perf.finish() only gets called in the callback that only gets called when the scheduler decides to call it:

mapbox-gl-js/src/source/vector_tile_worker_source.js

Line 196 in 47d8d51

const resourceTimingData = perf.finish();

mapbox-gl-js/src/source/vector_tile_worker_source.js

Lines 57 to 59 in 47d8d51

	this.scheduler.add(() => {
	callback(err, result);
	}, metadata);

This means it might be delayed significantly for some request types.

Fixing this might involve moving the perf = new RequestPerformance(...) and perf.finish() into DedupedRequest. I think this might also avoid the underlying issue in this pr.

But I'm also not fully sure how this specific metric is used so we should look at that more carefully at some point.

[ansis]

Could we get rid of the RequestPerformance class and replace it with a method that does what getMeasurement() does?

Both here and in geojson_worker_source.js we could do something like this:

_resourceTiming: getResourceTiming(params.request)

and remove the:

• new RequestPerformance()
• the stuff in DedupedRequest

[ryanhamley]

Yep 👍 much simpler