Filed by: aiakab [at] mozilla.com
Parsed log: https://treeherder.mozilla.org/logviewer.html#?job_id=261667353&repo=autoland
Full log: https://queue.taskcluster.net/v1/task/CuWCcnyMSuKBiWt7pEDBSQ/runs/0/artifacts/public/logs/live_backing.log
Reftest URL: https://hg.mozilla.org/mozilla-central/raw-file/tip/layout/tools/reftest/reftest-analyzer.xhtml#logurl=https://queue.taskcluster.net/v1/task/CuWCcnyMSuKBiWt7pEDBSQ/runs/0/artifacts/public/logs/live_backing.log&only_show_unexpected=1

[task 2019-08-14T21:34:49.729Z] 21:34:49 INFO - REFTEST TEST-START | file:///builds/worker/workspace/build/tests/reftest/tests/layout/reftests/text-decoration/decoration-color-standards.html == file:///builds/worker/workspace/build/tests/reftest/tests/layout/reftests/text-decoration/decoration-color-standards-ref.html
[task 2019-08-14T21:34:49.729Z] 21:34:49 INFO - REFTEST TEST-LOAD | file:///builds/worker/workspace/build/tests/reftest/tests/layout/reftests/text-decoration/decoration-color-standards.html | 3 / 116 (2%)
[task 2019-08-14T21:34:49.753Z] 21:34:49 INFO - REFTEST TEST-LOAD | file:///builds/worker/workspace/build/tests/reftest/tests/layout/reftests/text-decoration/decoration-color-standards-ref.html | 3 / 116 (2%)
[task 2019-08-14T21:34:49.775Z] 21:34:49 INFO - REFTEST TEST-PASS | file:///builds/worker/workspace/build/tests/reftest/tests/layout/reftests/text-decoration/decoration-color-standards.html == file:///builds/worker/workspace/build/tests/reftest/tests/layout/reftests/text-decoration/decoration-color-standards-ref.html | image comparison, max difference: 0, number of differing pixels: 0
[task 2019-08-14T21:34:49.776Z] 21:34:49 INFO - REFTEST TEST-END | file:///builds/worker/workspace/build/tests/reftest/tests/layout/reftests/text-decoration/decoration-color-standards.html == file:///builds/worker/workspace/build/tests/reftest/tests/layout/reftests/text-decoration/decoration-color-standards-ref.html
[task 2019-08-14T21:34:49.793Z] 21:34:49 INFO - REFTEST TEST-START | file:///builds/worker/workspace/build/tests/reftest/tests/layout/reftests/text-decoration/decoration-style-quirks.html == file:///builds/worker/workspace/build/tests/reftest/tests/layout/reftests/text-decoration/decoration-style-quirks-ref.html
[task 2019-08-14T21:34:49.794Z] 21:34:49 INFO - REFTEST TEST-LOAD | file:///builds/worker/workspace/build/tests/reftest/tests/layout/reftests/text-decoration/decoration-style-quirks.html | 4 / 116 (3%)
[task 2019-08-14T21:34:49.802Z] 21:34:49 INFO - REFTEST TEST-LOAD | file:///builds/worker/workspace/build/tests/reftest/tests/layout/reftests/text-decoration/decoration-style-quirks-ref.html | 4 / 116 (3%)
[task 2019-08-14T21:34:49.822Z] 21:34:49 INFO - REFTEST TEST-PASS | file:///builds/worker/workspace/build/tests/reftest/tests/layout/reftests/text-decoration/decoration-style-quirks.html == file:///builds/worker/workspace/build/tests/reftest/tests/layout/reftests/text-decoration/decoration-style-quirks-ref.html | image comparison, max difference: 0, number of differing pixels: 0
[task 2019-08-14T21:34:49.822Z] 21:34:49 INFO - REFTEST TEST-END | file:///builds/worker/workspace/build/tests/reftest/tests/layout/reftests/text-decoration/decoration-style-quirks.html == file:///builds/worker/workspace/build/tests/reftest/tests/layout/reftests/text-decoration/decoration-style-quirks-ref.html
[task 2019-08-14T21:34:49.838Z] 21:34:49 INFO - REFTEST TEST-START | file:///builds/worker/workspace/build/tests/reftest/tests/layout/reftests/text-decoration/decoration-style-standards.html == file:///builds/worker/workspace/build/tests/reftest/tests/layout/reftests/text-decoration/decoration-style-standards-ref.html
[task 2019-08-14T21:34:49.839Z] 21:34:49 INFO - REFTEST TEST-LOAD | file:///builds/worker/workspace/build/tests/reftest/tests/layout/reftests/text-decoration/decoration-style-standards.html | 5 / 116 (4%)
[task 2019-08-14T21:34:49.850Z] 21:34:49 INFO - REFTEST TEST-LOAD | file:///builds/worker/workspace/build/tests/reftest/tests/layout/reftests/text-decoration/decoration-style-standards-ref.html | 5 / 116 (4%)
[task 2019-08-14T21:34:50.082Z] 21:34:50 INFO - REFTEST TEST-UNEXPECTED-FAIL | file:///builds/worker/workspace/build/tests/reftest/tests/layout/reftests/text-decoration/decoration-style-standards.html == file:///builds/worker/workspace/build/tests/reftest/tests/layout/reftests/text-decoration/decoration-style-standards-ref.html | image comparison, max difference: 255, number of differing pixels: 9
[task 2019-08-14T21:34:50.083Z] 21:34:50 INFO - REFTEST IMAGE 1 (TEST):

Maybe a regression from enabling text-decoration-skip-ink by default?

I'm guessing the styling in the test:

text-decoration-style: dotted;
text-decoration: underline line-through overline

implies text-decoration-skip-ink:none for some reason, whereas the reference that only has:

text-decoration: underline line-through overline

doesn't. Which seems a bit weird...

I'm guessing the styling in the test ... implies text-decoration-skip-ink:none for some reason

No, it doesn't imply that -- if it did, we'd be seeing this failure happen more often.

We've seen ink-skipping intermittently fail to happen elsewhere, too -- see bug 1574306.

In this case here, it looks like it only failed on the very final line (y and p in "style is specified"). And it looks like this is linux-only so far:
https://treeherder.mozilla.org/intermittent-failures.html#/bugdetails?startday=2019-08-13&endday=2019-08-16&tree=all&bug=1574031

We had a similar intermittent bug pop up yesterday. https://bugzilla.mozilla.org/show_bug.cgi?id=1574306

For both bugs, I can run them locally and it passes. So it's not that text-decoration-skip-ink: none is implied for one test case and not the other, instead it's a bug in the skip-ink code.

Talking to dholbert, I believe the plan is to give it a couple of days and monitor if any more bugs like these two pop up. If it's just a couple of bugs, we can add text-decoration-skip-ink: none to the files for now. Otherwise, we might look at temporarily preffing skip-ink off during reftests for some platforms.

(In reply to Daniel Holbert [:dholbert] from comment #3)

And it looks like this is linux-only so far:

Just got one Win7 instance of this issue, over on duplicate bug 1575252:
https://treeherder.mozilla.org/logviewer.html#?job_id=262485083&repo=autoland

https://hg.mozilla.org/mozilla-central/rev/eec51eb982bc

We are pretty sure that this test no longer needs ink skipping to be disabled,
as of bug 1574066.

Depends on D43642

https://hg.mozilla.org/mozilla-central/rev/dd2e31e2f833