Investigate flaky wpt/test-user-timing test

[mhdawson]

Version

master

Platform

arm + x64

Subsystem

wpt

What steps will reproduce the bug?

Run test wpt/test-user-timing - https://ci.nodejs.org/job/node-test-binary-arm-12+/12718/RUN_SUBSET=2,label=pi2-docker/testReport/(root)/test/wpt_test_user_timing/

How often does it reproduce? Is there a required condition?

intermittent

What is the expected behavior?

test passes

What do you see instead?

test fails

Additional information

No response

[mhdawson]

Also failed here: https://ci.nodejs.org/job/node-test-commit-freebsd/nodes=freebsd12-x64/41486/console

[mhdawson]

From the reliability report this is one of the most problematic intermittent tests causing CI failures with 9 reported failures.

[mhdawson]

PR to mark flaky - #41203

[joyeecheung]

https://ci.nodejs.org/job/node-test-binary-arm-12+/14763/RUN_SUBSET=0,label=pi3-docker/testReport/junit/(root)/test/wpt_test_user_timing_/

Not sure if it's the same issue, here is another failure, looks like the measurements have a slightly higher error than anticipated.

---- user_timing_exists.any.js ----
[PASS] self.performance.clearMeasures is defined.
{
  'idlharness.any.js': { skip: 'idlharness cannot recognize Node.js environment' },
  'invoke_with_timing_attributes.worker.js': { skip: 'importScripts not supported' },
  'performance-measure-invalid.worker.js': { skip: 'importScripts not supported' },
  'mark.any.js': {
    fail: {
      unexpected: [
        'assert_approx_equals: expected 6722.132648468018 +/- 20 but got 6698.316417694092'
      ]
    }
  }
}