This is the bug I filled yesterday on this:
https://bugs.chromium.org/p/chromium/issues/detail?id=700139

I looked at the machine but doesn't see anything that I can recognize as "wrong". 

The only thing I can do at this moment is simply re-provision the slave, thus making it impossible to investigate further. If this is acceptable, I am ready to execute this in next 10 minutes.

Reprovisioning slave161-c1 after go ahead form fserb@

slave161-c1 O> Deleting instance slave161-c1...
slave161-c1 O> Running: /usr/local/google/home/tandrii/google-cloud-sdk/bin/gcloud compute instances delete -q slave161-c1 --zone us-central1-c --project google.com:chromecompute
slave161-c1 O> Executing command: /usr/local/google/home/tandrii/google-cloud-sdk/bin/gcloud compute instances delete -q slave161-c1 --zone us-central1-c --project google.com:chromecompute
slave161-c1 O> == Output from command: /usr/local/google/home/tandrii/google-cloud-sdk/bin/gcloud compute instances delete -q slave161-c1 --zone us-central1-c --project google.com:chromecompute
slave161-c1 E> Deleted [https://www.googleapis.com/compute/v1/projects/google.com:chromecompute/zones/us-central1-c/instances/slave161-c1].
slave161-c1 O> Adding instance slave161-c1...
slave161-c1 O> Running: /usr/local/google/home/tandrii/google-cloud-sdk/bin/gcloud compute instances create slave161-c1 --machine-type n1-standard-8 --zone us-central1-c --project google.com:chromecompute --image chrome-trusty-16102500-3c5d0899e78 --image-project google.com:chromecompute --boot-disk-size 500GB --boot-disk-type pd-standard --address 104.154.8.172 --scopes https://www.googleapis.com/auth/devstorage.full_control,https://www.googleapis.com/auth/gerritcodereview,https://www.googleapis.com/auth/logging.write,https://www.googleapis.com/auth/monitoring,https://www.googleapis.com/auth/pubsub,https://www.googleapis.com/auth/userinfo.email --metadata image_name=chrome-trusty-16102500-3c5d0899e78 --metadata-from-file cipd_deployments=/usr/local/google/home/tandrii/s/infra_internal/infra_internal/ccompute/scripts/cipd/buildbot-trusty.json
slave161-c1 O> Executing command: /usr/local/google/home/tandrii/google-cloud-sdk/bin/gcloud compute instances create slave161-c1 --machine-type n1-standard-8 --zone us-central1-c --project google.com:chromecompute --image chrome-trusty-16102500-3c5d0899e78 --image-project google.com:chromecompute --boot-disk-size 500GB --boot-disk-type pd-standard --address 104.154.8.172 --scopes https://www.googleapis.com/auth/devstorage.full_control,https://www.googleapis.com/auth/gerritcodereview,https://www.googleapis.com/auth/logging.write,https://www.googleapis.com/auth/monitoring,https://www.googleapis.com/auth/pubsub,https://www.googleapis.com/auth/userinfo.email --metadata image_name=chrome-trusty-16102500-3c5d0899e78 --metadata-from-file cipd_deployments=/usr/local/google/home/tandrii/s/infra_internal/infra_internal/ccompute/scripts/cipd/buildbot-trusty.json
slave161-c1 O> == Output from command: /usr/local/google/home/tandrii/google-cloud-sdk/bin/gcloud compute instances create slave161-c1 --machine-type n1-standard-8 --zone us-central1-c --project google.com:chromecompute --image chrome-trusty-16102500-3c5d0899e78 --image-project google.com:chromecompute --boot-disk-size 500GB --boot-disk-type pd-standard --address 104.154.8.172 --scopes https://www.googleapis.com/auth/devstorage.full_control,https://www.googleapis.com/auth/gerritcodereview,https://www.googleapis.com/auth/logging.write,https://www.googleapis.com/auth/monitoring,https://www.googleapis.com/auth/pubsub,https://www.googleapis.com/auth/userinfo.email --metadata image_name=chrome-trusty-16102500-3c5d0899e78 --metadata-from-file cipd_deployments=/usr/local/google/home/tandrii/s/infra_internal/infra_internal/ccompute/scripts/cipd/buildbot-trusty.json
slave161-c1 O> NAME         ZONE           MACHINE_TYPE   PREEMPTIBLE  INTERNAL_IP  EXTERNAL_IP    STATUS
slave161-c1 O> slave161-c1  us-central1-c  n1-standard-8               10.240.0.22  104.154.8.172  RUNNING
slave161-c1 E> Created [https://www.googleapis.com/compute/v1/projects/google.com:chromecompute/zones/us-central1-c/instances/slave161-c1].

Slave will be back soon. If this solves the problem, then it the bot got corrupted.
If this doesn't solve the problem, then there was some either infra or code change that is clearly reproducible.

Bot is back on, it's still failing, so it is definitely not a bot issue.

The failures are:

Regressions: Unexpected timeouts (5)
  external/wpt/dom/events/EventListener-invoke-legacy.html [ Timeout ]
  external/wpt/svg/interfaces.html [ Timeout ]
  webaudio/BiquadFilter/biquad-automation.html [ Timeout ]
  webaudio/IIRFilter/iirfilter.html [ Timeout ]

Some more output here:

13:48:16.373 5148 worker/1 webaudio/IIRFilter/iirfilter.html output stderr lines:
13:48:16.373 5148   Xlib:  extension "RANDR" missing on display ":9".
13:48:16.375 22877 [11/11] webaudio/IIRFilter/iirfilter.html failed unexpectedly (test timed out)

-Trooper

Actually that looks like a red herring, since it's printed everywhere.

They look like truely flaky tests.  Not much a trooper can do at this point.

I filed a related bug for a subset of the tests that are crashing on MSAN:  bug 701170 , and uploaded a CL to add expectations: https://codereview.chromium.org/2751563003.

Alright, at this point, since  bug 701170  is fixed, we now have several timeout issues with particular tests:

These have timed out since they were first added (sometimes flakily, sometimes passing), but only on the MSAN bot:

external/wpt/dom/events/EventListener-invoke-legacy.html
external/wpt/svg/interfaces.html

This times out for as long as the flakiness dashboard shows (just a few days), sometimes flakily:

webaudio/IIRFilter/iirfilter.html
webaudio/AudioParam/audioparam-method-chaining.html

This one appears to have started timing out just recently:

webaudio/BiquadFilter/biquad-automation.html

This has timed out recently, but also flakily timed out before:

crypto/subtle/worker-subtle-crypto-concurrent.html

Next step: Adding flaky timeout + slow expectations in MSANExpectations, and perhaps filing individual bugs?

MSAN builder is green again for now:
https://build.chromium.org/p/chromium.webkit/builders/WebKit%20Linux%20Trusty%20MSAN