I also see "ls: cannot access '/sys/devices/system/cpu/cpu*/cpufreq/cpuinfo_max_freq': No such file or directory" errors at the very top of the log. Is that or the "measurements.rendering_unittest.RenderingUnitTest.testRendering" causing the build to fail? I can't really tell.

For the "cpuinfo_max_freq" failure: digging through the stack trace shows that this condition is false:
https://cs.corp.google.com/chromeos_public/src/third_party/autotest/files/client/bin/utils.py?rcl=1001ab7c0caa6a1b50da14929554781eccfd174e&l=2062

This is a vm test, right? Surely it should be true?

And querying buildbucket's api, the last successful build is:
https://ci.chromium.org/p/chromeos/builds/b8944404981669940720

The first failing build is:
https://ci.chromium.org/p/chromeos/builds/b8944393850128884704

Not sure if that helps

I believe that the cpuinfo_max_freq failure is innocuous. e.g. see issue 594569. We should prioritize fixing that, confusing errors cost us time, but I don't think that is the cause of the failure.

I'll try to look at the CrOS and Chrome changes between those builds to see if there is a smoking gun.

I think my CL, that introduced the test, is the culprit: https://chromium-review.googlesource.com/c/chromium/src/+/1054253.

I will revert it.

Ehsan: I suggest just disable the test on CHromeOS then investigate it instead of reverting 

The following revision refers to this bug:
  https://chromium.googlesource.com/chromium/src.git/+/33f0cdf5dbfbba5e526524ca350a386829262c1c

commit 33f0cdf5dbfbba5e526524ca350a386829262c1c
Author: Ehsan Chiniforooshan <chiniforooshan@chromium.org>
Date: Mon Jun 11 21:10:06 2018

Telemetry: disable testRendering on CrOS

Bug:  851523 
Change-Id: Ic8b38c700729445cfc59968f57361b5e4f476201
Reviewed-on: https://chromium-review.googlesource.com/1095652
Commit-Queue: Ehsan Chiniforooshan <chiniforooshan@chromium.org>
Commit-Queue: Achuith Bhandarkar <achuith@chromium.org>
Reviewed-by: Achuith Bhandarkar <achuith@chromium.org>
Cr-Commit-Position: refs/heads/master@{#566145}
[modify] https://crrev.com/33f0cdf5dbfbba5e526524ca350a386829262c1c/tools/perf/measurements/rendering_unittest.py

The problem is that the browser is not closed after each run on CrOS:

https://cs.chromium.org/chromium/src/third_party/catapult/telemetry/telemetry/page/shared_page_state.py?l=177

So, when pageset_repeat is more than 1, at the 2nd and later runs, the page is already scrolled down, which means 2nd and later runs don't generate animations.

One way to fix, other than closing the browser at the end of each run, is that the test PageTest undo the scroll at the end: crrev.com/c/1097624. I verified that the patch fixes the test on CrOS.

The following revision refers to this bug:
  https://chromium.googlesource.com/catapult/+/0db1e01e3f4c793433cc31be9aef39c4deb1cbe3

commit 0db1e01e3f4c793433cc31be9aef39c4deb1cbe3
Author: Ehsan Chiniforooshan <chiniforooshan@chromium.org>
Date: Wed Jun 13 06:05:01 2018

Telemetry: Scroll up at the end of test PageTests

The browser is left open after each run on CrOS:

https://cs.chromium.org/chromium/src/third_party/catapult/telemetry/telemetry/page/shared_page_state.py?l=177

So, for example, when pageset_repeat is more than 1, at the 2nd and
later runs, the page is already scrolled down, which means 2nd and
later runs don't generate animations. This can cause tests that set
pagetest_repeat to more than 1 see unexpected results.

One way to fix, other than closing the browser at the end of each run,
is to make sure that the test PageTest undoes the scroll at the end.

Bug:  chromium:851523 
Change-Id: I086c78beab8f1306a52a31fd9de4bfaf70e147b6
Reviewed-on: https://chromium-review.googlesource.com/1097624
Commit-Queue: Ehsan Chiniforooshan <chiniforooshan@chromium.org>
Reviewed-by: Ned Nguyen <nednguyen@google.com>

[modify] https://crrev.com/0db1e01e3f4c793433cc31be9aef39c4deb1cbe3/telemetry/telemetry/testing/page_test_test_case.py

The following revision refers to this bug:
  https://chromium.googlesource.com/chromium/src.git/+/8eb26b017ab5cc7e36cf1fdf6f8a3e70f519eeb0

commit 8eb26b017ab5cc7e36cf1fdf6f8a3e70f519eeb0
Author: catapult-chromium-autoroll <catapult-chromium-autoroll@skia-buildbots.google.com.iam.gserviceaccount.com>
Date: Wed Jun 13 10:25:42 2018

Roll src/third_party/catapult 459c4d0417df..0db1e01e3f4c (1 commits)

https://chromium.googlesource.com/catapult.git/+log/459c4d0417df..0db1e01e3f4c


git log 459c4d0417df..0db1e01e3f4c --date=short --no-merges --format='%ad %ae %s'
2018-06-13 chiniforooshan@chromium.org Telemetry: Scroll up at the end of test PageTests


Created with:
  gclient setdep -r src/third_party/catapult@0db1e01e3f4c

The AutoRoll server is located here: https://catapult-roll.skia.org

Documentation for the AutoRoller is here:
https://skia.googlesource.com/buildbot/+/master/autoroll/README.md

If the roll is causing failures, please contact the current sheriff, who should
be CC'd on the roll, and stop the roller if necessary.

CQ_INCLUDE_TRYBOTS=luci.chromium.try:android_optional_gpu_tests_rel;luci.chromium.try:linux_optional_gpu_tests_rel;luci.chromium.try:mac_optional_gpu_tests_rel;luci.chromium.try:win_optional_gpu_tests_rel

BUG= chromium:851523 
TBR=sullivan@chromium.org

Change-Id: I9c73ab9c69c2ce98c120ed1a97cf298cdafdf84d
Reviewed-on: https://chromium-review.googlesource.com/1098715
Reviewed-by: catapult-chromium-autoroll <catapult-chromium-autoroll@skia-buildbots.google.com.iam.gserviceaccount.com>
Commit-Queue: catapult-chromium-autoroll <catapult-chromium-autoroll@skia-buildbots.google.com.iam.gserviceaccount.com>
Cr-Commit-Position: refs/heads/master@{#566787}
[modify] https://crrev.com/8eb26b017ab5cc7e36cf1fdf6f8a3e70f519eeb0/DEPS

The following revision refers to this bug:
  https://chromium.googlesource.com/chromium/src.git/+/0f129a2afc040498dd29fd1df47202aa4959db63

commit 0f129a2afc040498dd29fd1df47202aa4959db63
Author: Ehsan Chiniforooshan <chiniforooshan@chromium.org>
Date: Wed Jun 13 19:02:27 2018

Telemetry: re-enable testRendering on CrOS

The fix (crrev.com/c/1097624) is already rolled (crrev.com/c/1098715)

Bug:  851523 
Change-Id: I6a4f35eb1448b14c2a28864236bcde9785ee768a
Reviewed-on: https://chromium-review.googlesource.com/1098634
Reviewed-by: Achuith Bhandarkar <achuith@chromium.org>
Commit-Queue: Ehsan Chiniforooshan <chiniforooshan@chromium.org>
Cr-Commit-Position: refs/heads/master@{#566937}
[modify] https://crrev.com/0f129a2afc040498dd29fd1df47202aa4959db63/tools/perf/measurements/rendering_unittest.py