Cluprit CL shouldn't have an impact on this and I couldn't repro locally but then I started another build on my machine and the test started failing. It seems like content_shell is pinned at 100% during this test and if it has to compete for CPU time, it's likely to time out.

Digging a bit further.

When it passes this test take 17.4s, the timeout is 18s. Gonna mark it as a slow test.

Going back ~300 commits, this was still slow.

 Issue 897849  has been merged into this issue.

cc oksamyt who submitted the culprit. That patch is mojom related so maybe oksamyt@ has inputs regarding the racing here.

The test was very slow before that cl too. I don't think the mojom stuff is
connected TBH

Right. According to [1] it was slow before that patch.

[1] https://test-results.appspot.com/dashboards/flakiness_dashboard.html#testType=webkit_layout_tests&showExpectations=true&tests=accessibility%2Ftable-header-column-row.html

Possible regression range is:
https://chromium.googlesource.com/chromium/src/+log/f0536f4628fc12b899481c592e7672740b871981%5E..02b6cf719bbc4f9b7e792b760c91c2dd50f7b4d6?pretty=fuller&n=

Note that there was a v8 roll within that range which has caused other tests flaky. See  issue 898062 .

r601651 changes a build target's dependencies and shouldn't influence anything in runtime, so I agree it's unlikely to be related to the slow/flaky tests.

Looks like the test was already marked flaky in  bug 897849 .

The test is just slow, on the borderline of the timeout. I've sent a CL to mark it as a slow test so that the timeout is much larger.

https://crrev.com/c/1295758

accessibility/table-header-column-row.html is flaky.

Findit has detected 8 new flake occurrences of this test. List
of all flake occurrences can be found at:
https://findit-for-me.appspot.com/flake/occurrences?key=ag9zfmZpbmRpdC1mb3ItbWVyUgsSBUZsYWtlIkdjaHJvbWl1bUB3ZWJraXRfbGF5b3V0X3Rlc3RzQGFjY2Vzc2liaWxpdHkvdGFibGUtaGVhZGVyLWNvbHVtbi1yb3cuaHRtbAw.

Since this test is still flaky, this issue has been moved back onto the Sheriff
Bug Queue if it's not already there.

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%20for%20accessibility/table-header-column-row.html&comment=Link%20to%20flake%20occurrences%3A%20https://findit-for-me.appspot.com/flake/occurrences?key=ag9zfmZpbmRpdC1mb3ItbWVyUgsSBUZsYWtlIkdjaHJvbWl1bUB3ZWJraXRfbGF5b3V0X3Rlc3RzQGFjY2Vzc2liaWxpdHkvdGFibGUtaGVhZGVyLWNvbHVtbi1yb3cuaHRtbAw

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

Actually this slowness is due to something funny with .innerText. I have filed https://crbug.com/900098 with a simple repro case.

The following revision refers to this bug:
  https://chromium.googlesource.com/chromium/src.git/+/6637b4ee2b61bcf6dbf2ae3fa0a0010198ee80b0

commit 6637b4ee2b61bcf6dbf2ae3fa0a0010198ee80b0
Author: Fergal Daly <fergal@chromium.org>
Date: Tue Oct 30 14:00:46 2018

Repeatedly appending to .innerText is slow and causing timeouts.

Change the code to build an array of strings and then use join to
avoid repeated appends.

Bug:  898049 
Change-Id: I194a9da3444d097dd30f4738a795391f44c6a22b
Reviewed-on: https://chromium-review.googlesource.com/c/1306965
Reviewed-by: Yoshifumi Inoue <yosin@chromium.org>
Reviewed-by: Aaron Leventhal <aleventhal@chromium.org>
Commit-Queue: Fergal Daly <fergal@chromium.org>
Cr-Commit-Position: refs/heads/master@{#603884}
[modify] https://crrev.com/6637b4ee2b61bcf6dbf2ae3fa0a0010198ee80b0/third_party/WebKit/LayoutTests/resources/accessibility-helper.js

 Issue 899885  has been merged into this issue.

Merge  issue 899885  as this test was also failed on Win7. However, if the patch above has fixed the issue, please enable these two tests.

 Issue 900311  has been merged into this issue.

The following revision refers to this bug:
  https://chromium.googlesource.com/chromium/src.git/+/2be6c3e2c1e468074a8eaa71d61345403c7d20ee

commit 2be6c3e2c1e468074a8eaa71d61345403c7d20ee
Author: Fergal Daly <fergal@chromium.org>
Date: Wed Oct 31 04:19:07 2018

Remove flaky test entry for 2 accessibility tests.
 * accessibility/element-role-mapping-normal.html
 * accessibility/table-header-column-row.html

The flakiness is due to slowness which is fixed by
https://crrev.com/c/1306965


Bug:  898049 , 899885 
Change-Id: If4a9a770833344b3b55e89bbc3379f3cc9560e0e
Reviewed-on: https://chromium-review.googlesource.com/c/1309375
Reviewed-by: Yi Gu <yigu@chromium.org>
Commit-Queue: Fergal Daly <fergal@chromium.org>
Cr-Commit-Position: refs/heads/master@{#604145}
[modify] https://crrev.com/2be6c3e2c1e468074a8eaa71d61345403c7d20ee/third_party/WebKit/LayoutTests/TestExpectations