There is one other recent run showing the same 3 tests failing:

Unexpected Failures:
* telemetry.core.tracing_controller_unittest.TracingControllerTest.testFlushTracing
* telemetry.page.cache_temperature_unittest.CacheTemperatureTests.testEnsureHotAfterColdAndWarmRun
* telemetry.page.cache_temperature_unittest.CacheTemperatureTests.testEnsureWarmAfterColdRun
 

https://ci.chromium.org/p/chromium/builders/luci.chromium.try/linux_chromium_rel_ng/130078

I see error logs like below which make me think there could have been an infra problem.

[1:1:0628/175626.665629:ERROR:memory_mapped_file.cc(53)] Couldn't open /b/s/w/ir/out/Release/chrome_200_percent.pak

Both of these failures happened on the same server:
https://chromium.googlesource.com/infra/luci/luci-py/+/21ffa58

Assigning to Infra-Troopers

Failures at:

https://chromium-swarm.appspot.com/task?id=3e61d87b89cc7710&refresh=10&show_raw=1
https://chromium-swarm.appspot.com/task?id=3e6200583aa99f10&refresh=10&show_raw=1

#2: These look like pretty standard test flakes. Pretty sure the chrome_200_percent.pak log message is a red herring. Not sure what you mean by the "same server" thing.

Back to sheriffs.

Juan: can you own TracingControllerTest since you added it recently?

Looks like an issue with tracing. But couldn't find more examples of this issue happening. I'll check back again on a couple of days to see if the flakes persist.

Also, is this really blocking issue 840033?

telemetry_unittests isn't showing failure on last 200 builds, so removing from sheriff queue.

https://ci.chromium.org/p/chromium/builders/luci.chromium.try/linux_chromium_rel_ng
?limit=200

The NextAction date has arrived: 2018-07-04

Still no new flakes. Closing. If this re-occurs it will be hopefully caught by the flakiness dashboard.

Thanks for investigating. Wasn't really blocking Issue 840033, but wanted to establish some link between these two similar bugs.