Time Origin in Workers - official moment of creation or not?

[JosephPecoraro]

The spec specifically mentions that the time origin for Workers:

The time origin is the time value from which time is measured:

• If the global object is a WorkerGlobalScope object, the time origin must be equal to the official moment of creation of the worker.

This doesn't appear to match implementations. For example:

<script>
let blob = new Blob([`console.log(performance.now())`]);
let url = URL.createObjectURL(blob);
console.log(performance.now());
setTimeout(() => { worker = new Worker(url); }, 1000);
</script>

Based on the spec, I would expect very low numbers for both logs. The one on the page because it is very close to the page's load. The one in the worker because it is very close to the worker's load.

Implementations are consistent but differ from the spec:

• Chrome (v55)
  page: 13.495
  worker: 1047.71

• Firefox (v51)
  page: 17.135
  worker: 1032.125

I am unable to test on Edge. If someone could include their numbers that would be fantastic!

[JosephPecoraro]

It may make sense for a DedicatedWebWorker's time origin to match the Document that spawned it. That would make it so developers can more easily reason about timestamps gathered in both the document and its workers. This convenience breaks down for SharedWorkers, so I would say it is not worth making different behavior for different types of Workers.

I suggest keeping the spec as is, filing bugs on browsers, and adding a web platform test to cover this. But I want to make sure my interpretation of the spec and test case is correct.

[igrigorik]

I suggest keeping the spec as is, filing bugs on browsers, and adding a web platform test to cover this. But I want to make sure my interpretation of the spec and test case is correct.

It is. You can scrub through the past conversations on translateTime to see us covering the same points.. Also why we introduced https://w3c.github.io/hr-time/#dom-performance-timeorigin in L3.

WPT tests + bugs is the right path forward.

[JosephPecoraro]

Chrome Bug: https://bugs.chromium.org/p/chromium/issues/detail?id=688542
Firefox Bug: https://bugzilla.mozilla.org/show_bug.cgi?id=1336595