Does this happen on any other platform?

I don't know, I only watch the Cronet bots. The other bug I linked looks like it's talking about a Linux failure, though, so if they're actually related then yes.

The android_n5x_swarming_rel trybot reports several flakes in  bug 646180  and  bug 646181 .

I'm also seeing similar failures on the Android N5X Swarm Builder starting with https://build.chromium.org/p/chromium.android/builders/Android%20N5X%20Swarm%20Builder/builds/4088
For this, I'm unable to see a culprit CL in the change log that could explain this. Please investigate.

Summary of failing tests:
CertNetFetcherImplTest.FetchWithinCallback
CertNetFetcherImplTest.CancelBeforeRunningMessageLoop
CertNetFetcherImplTest.CancelLastRequestWithinCallback
CertNetFetcherImplTest.CancelThenStart
CertNetFetcherImplTest.ParallelFetchNoDuplicates
CertNetFetcherImplTest.ParallelFetchDuplicates

 Issue 646180  has been merged into this issue.

 Issue 646181  has been merged into this issue.

The following revision refers to this bug:
  https://chromium.googlesource.com/chromium/src.git/+/4f4fb6562bf120882b215644ebab78d0a5d226ce

commit 4f4fb6562bf120882b215644ebab78d0a5d226ce
Author: kjellander <kjellander@chromium.org>
Date: Tue Sep 13 08:20:58 2016

Disable CertNetFetcherImplTest tests on Android

The following tests are flaky on Android:
CertNetFetcherImplTest.FetchWithinCallback
CertNetFetcherImplTest.CancelBeforeRunningMessageLoop
CertNetFetcherImplTest.CancelLastRequestWithinCallback
CertNetFetcherImplTest.CancelThenStart
CertNetFetcherImplTest.ParallelFetchNoDuplicates
CertNetFetcherImplTest.ParallelFetchDuplicates

This seems to have started with https://build.chromium.org/p/chromium.android/builders/Android%20N5X%20Swarm%20Builder/builds/4088

BUG= 646147 
TBR=eroman@chromium.org

Review-Url: https://codereview.chromium.org/2338713002
Cr-Commit-Position: refs/heads/master@{#418195}

[modify] https://crrev.com/4f4fb6562bf120882b215644ebab78d0a5d226ce/net/cert_net/cert_net_fetcher_impl_unittest.cc

 Issue 646303  has been merged into this issue.

 Issue 646302  has been merged into this issue.

 Issue 646318  has been merged into this issue.

Detected 4 new flakes for test/step "CertNetFetcherImplTest.FetchWithinCallback". To see the actual flakes, please visit https://chromium-try-flakes.appspot.com/all_flake_occurrences?key=ahVzfmNocm9taXVtLXRyeS1mbGFrZXNyNQsSBUZsYWtlIipDZXJ0TmV0RmV0Y2hlckltcGxUZXN0LkZldGNoV2l0aGluQ2FsbGJhY2sM. This message was posted automatically by the chromium-try-flakes app. Since flakiness is ongoing, the issue was moved back into Sheriff Bug Queue (unless already there).

Detected 4 new flakes for test/step "CertNetFetcherImplTest.CancelBeforeRunningMessageLoop". To see the actual flakes, please visit https://chromium-try-flakes.appspot.com/all_flake_occurrences?key=ahVzfmNocm9taXVtLXRyeS1mbGFrZXNyQAsSBUZsYWtlIjVDZXJ0TmV0RmV0Y2hlckltcGxUZXN0LkNhbmNlbEJlZm9yZVJ1bm5pbmdNZXNzYWdlTG9vcAw. This message was posted automatically by the chromium-try-flakes app.

Taking off sheriff queue since this is assigned and being worked on.

 Issue 646215  has been merged into this issue.

Will re-enable to gather new data.

The implementation of these tests is now significantly different. I hadn't identified what the original problem was, but I suspect it had to do with the test setup itself in running message loop till idle (which is no longer done).

The following revision refers to this bug:
  https://chromium.googlesource.com/chromium/src.git/+/fd77cd1bc5dd1e55d1c68f4c99f52a782daad299

commit fd77cd1bc5dd1e55d1c68f4c99f52a782daad299
Author: eroman <eroman@chromium.org>
Date: Wed Nov 30 07:55:14 2016

Un-disable CertNetFetcherImplTests on Android.

(Suspect it is no longer flaky)

BUG= 646147 

Review-Url: https://codereview.chromium.org/2540543003
Cr-Commit-Position: refs/heads/master@{#435145}

[modify] https://crrev.com/fd77cd1bc5dd1e55d1c68f4c99f52a782daad299/net/cert_net/cert_net_fetcher_impl_unittest.cc