The linked CL only changes flag metadata.

Filed Wrong culprit bug report at https://bugs.chromium.org/p/chromium/issues/detail?id=922416

Findit identified the culprit r622514 as introducing flaky test(s)
summarized in https://findit-for-me.appspot.com/waterfall/flake/flake-culprit?key=ag9zfmZpbmRpdC1mb3ItbWVyQwsSDEZsYWtlQ3VscHJpdCIxY2hyb21pdW0vZDI4OWNjM2QxODEzM2IyMTQzNDM4MTM1NzhiZDcxYmM0ODgzNzMwNQw

Please revert the culprit or disable the test(s) asap. If you are the owner,
please fix!

If the culprit above is wrong, please file a bug using this link:
https://bugs.chromium.org/p/chromium/issues/entry?status=Unconfirmed&labels=Pri-1,Test-Findit-Wrong&components=Tools%3ETest%3EFindit%3EFlakiness&summary=%5BFindit%5D%20Flake%20Analyzer%20-%20Wrong%20culprit%20r622514&comment=Link%20to%20Culprit%3A%20https://findit-for-me.appspot.com/waterfall/flake/flake-culprit?key=ag9zfmZpbmRpdC1mb3ItbWVyQwsSDEZsYWtlQ3VscHJpdCIxY2hyb21pdW0vZDI4OWNjM2QxODEzM2IyMTQzNDM4MTM1NzhiZDcxYmM0ODgzNzMwNQw

Automatically posted by the findit-for-me app (https://goo.gl/Ot9f7N).

WorkletAnimationTest.CurrentTimeFromDocumentTimelineIsOffsetByStartTime is flaky.

Findit has detected 4 new flake occurrences of this test. List
of all flake occurrences can be found at:
https://findit-for-me.appspot.com/flake/occurrences?key=ag9zfmZpbmRpdC1mb3ItbWVybQsSBUZsYWtlImJjaHJvbWl1bUB3ZWJraXRfdW5pdF90ZXN0c0BXb3JrbGV0QW5pbWF0aW9uVGVzdC5DdXJyZW50VGltZUZyb21Eb2N1bWVudFRpbWVsaW5lSXNPZmZzZXRCeVN0YXJ0VGltZQw.

Since these tests are still flaky, this issue has been moved back onto the Sheriff Bug Queue if it hasn't already.

If the result above is wrong, please file a bug using this link:
https://bugs.chromium.org/p/chromium/issues/entry?status=Unconfirmed&labels=Pri-1,Test-Findit-Wrong&components=Tools%3ETest%3EFindit%3EFlakiness&summary=%5BFindit%5D%20Flake%20Detection%20-%20Wrong%20result%3A%20WorkletAnimationTest.CurrentTimeFromDocumentTimelineIsOffsetByStartTime&comment=Link%20to%20flake%20details%3A%20https://findit-for-me.appspot.com/flake/occurrences?key=ag9zfmZpbmRpdC1mb3ItbWVybQsSBUZsYWtlImJjaHJvbWl1bUB3ZWJraXRfdW5pdF90ZXN0c0BXb3JrbGV0QW5pbWF0aW9uVGVzdC5DdXJyZW50VGltZUZyb21Eb2N1bWVudFRpbWVsaW5lSXNPZmZzZXRCeVN0YXJ0VGltZQw

Automatically posted by the findit-for-me app (https://goo.gl/Ot9f7N).

I am now looking into this.

The test is trying to compare two time values and expects a certain amount of error (1us). The patch is changing our internal representation of current time to be a TimeDelta instead of a double but then the time is converted to double before it is sent to the worklet.

So the change can affect our precision since it introduces additional conversions. Ultimately we should avoid converting to double and keep sending the TimeDelta to the worklet [1] but in the meantime we can improve the test.


[1] https://chromium-review.googlesource.com/c/chromium/src/+/1397846/9/third_party/blink/renderer/modules/animationworklet/worklet_animation.cc#576l




Here is an example failure: 

[ RUN      ] WorkletAnimationTest.CurrentTimeFromDocumentTimelineIsOffsetByStartTime
../../third_party/blink/renderer/modules/animationworklet/worklet_animation_test.cc:130: Failure
The difference between 123.4 and input->updated_animations[0].current_time is 0.0010000000000047748, which exceeds error, where
123.4 evaluates to 123.40000000000001,
input->updated_animations[0].current_time evaluates to 123.399, and
error evaluates to 0.001.
Stack trace:
#0 0x56390a8e1772 testing::internal::UnitTestImpl::CurrentOsStackTraceExceptTop()
#1 0x56390a8e13d1 testing::internal::AssertHelper::operator=()
#2 0x56390b793e3a blink::WorkletAnimationTest_CurrentTimeFromDocumentTimelineIsOffsetByStartTime_Test::TestBody()

[  FAILED  ] WorkletAnimationTest.CurrentTimeFromDocumentTimelineIsOffsetByStartTime (12 ms)

 Issue 922607  has been merged into this issue.

 Issue 921897  has been merged into this issue.

The following revision refers to this bug:
  https://chromium.googlesource.com/chromium/src.git/+/10b5e48292eec73e2c523b6684c2e8677fcf0158

commit 10b5e48292eec73e2c523b6684c2e8677fcf0158
Author: Majid Valipour <majidvp@chromium.org>
Date: Wed Jan 16 23:18:14 2019

Improve WorkletAnimationTest to reduce flakiness

 - Increase expected timing error by a small amount to take into account
   double rounding issues.
 - Use AnimationClock::ResetTimeForTesting to ensure we are not going to
   ever depend on wall clock. This is unrelated to flakiness but just a
   cleanup.

Also I re-enabled incorrectly disabled test (that had the same name). To
avoid future confusion, change the cc side name. [1]

[1] https://bugs.chromium.org/p/chromium/issues/detail?id=921897#c5

TEST: Locally ran the test 500 times successfully (previously failed at least 1 out of 100)
TBR: flackr@chromium.org
Bug:  921835 
Change-Id: I29e03db25122e63660877ee64145252c1d258564
Reviewed-on: https://chromium-review.googlesource.com/c/1416290
Reviewed-by: Majid Valipour <majidvp@chromium.org>
Reviewed-by: Yi Gu <yigu@chromium.org>
Commit-Queue: Majid Valipour <majidvp@chromium.org>
Cr-Commit-Position: refs/heads/master@{#623435}
[modify] https://crrev.com/10b5e48292eec73e2c523b6684c2e8677fcf0158/cc/animation/worklet_animation_unittest.cc
[modify] https://crrev.com/10b5e48292eec73e2c523b6684c2e8677fcf0158/third_party/blink/renderer/modules/animationworklet/worklet_animation_test.cc

WorkletAnimationTest.CurrentTimeFromDocumentTimelineIsOffsetByStartTime is flaky.

Findit has detected 6 new flake occurrences of this test. List
of all flake occurrences can be found at:
https://findit-for-me.appspot.com/flake/occurrences?key=ag9zfmZpbmRpdC1mb3ItbWVybQsSBUZsYWtlImJjaHJvbWl1bUB3ZWJraXRfdW5pdF90ZXN0c0BXb3JrbGV0QW5pbWF0aW9uVGVzdC5DdXJyZW50VGltZUZyb21Eb2N1bWVudFRpbWVsaW5lSXNPZmZzZXRCeVN0YXJ0VGltZQw.

Since these tests are still flaky, this issue has been moved back onto the Sheriff Bug Queue if it hasn't already.

If the result above is wrong, please file a bug using this link:
https://bugs.chromium.org/p/chromium/issues/entry?status=Unconfirmed&labels=Pri-1,Test-Findit-Wrong&components=Tools%3ETest%3EFindit%3EFlakiness&summary=%5BFindit%5D%20Flake%20Detection%20-%20Wrong%20result%3A%20WorkletAnimationTest.CurrentTimeFromDocumentTimelineIsOffsetByStartTime&comment=Link%20to%20flake%20details%3A%20https://findit-for-me.appspot.com/flake/occurrences?key=ag9zfmZpbmRpdC1mb3ItbWVybQsSBUZsYWtlImJjaHJvbWl1bUB3ZWJraXRfdW5pdF90ZXN0c0BXb3JrbGV0QW5pbWF0aW9uVGVzdC5DdXJyZW50VGltZUZyb21Eb2N1bWVudFRpbWVsaW5lSXNPZmZzZXRCeVN0YXJ0VGltZQw

Automatically posted by the findit-for-me app (https://goo.gl/Ot9f7N).

Looking at the flakes referred to in #10 they are from builds that don't include the patch.

So far looking at the dashboard it seems that the fix is effective but it will be a while before we know for sure: 
https://test-results.appspot.com/dashboards/flakiness_dashboard.html#testType=webkit_unit_tests&tests=WorkletAnimationTest.CurrentTimeFromDocumentTimelineIsOffsetByStartTime

Thanks, Majid -- going to remove from the sheriff queue then. If it flakes again, sheriffs should see this come back up.