It might be good to post some more info:

There's:

06/25 05:53:55.691 ERROR|         traceback:0013| CmdError: Command <ls /sys/devices/system/cpu/cpu*/cpufreq/cpuinfo_max_freq> failed, rc=2, Command returned non-zero exit status
06/25 05:53:55.694 ERROR|         traceback:0013| * Command: 

Which looks unrelated but definitely adds noise to the logs.

The failure is:

estFail: Unable to parse fail reason: Command <su chronos -c 'HOME=/tmp/tmp2YmcGJ CR_SOURCE_ROOT=/usr/local/autotest/deps/chrome_test/test_src CHROME_DEVEL_SANDBOX=/opt/google/chrome/chrome-sandbox GTEST_OUTPUT=xml:/tmp/gtest_xml4d60oj.xml /usr/local/autotest/deps/chrome_test/test_src/out/Release/sandbox_linux_unittests '> failed, rc=1, Command returned non-zero exit status
* Command: 
    su chronos -c 'HOME=/tmp/tmp2YmcGJ
    CR_SOURCE_ROOT=/usr/local/autotest/deps/chrome_test/test_src
    CHROME_DEVEL_SANDBOX=/opt/google/chrome/chrome-sandbox
    GTEST_OUTPUT=xml:/tmp/gtest_xml4d60oj.xml /usr/local/autotest/deps/chrome_
    test/test_src/out/Release/sandbox_linux_unittests '
Exit status: 1

And there is:
Failed to get out-of-band test success data, dumping full stdio below:
[30752:30752:0625/055355.748222:2133233827:ERROR:icu_util.cc(172)] Invalid file descriptor to ICU data received.

Any idea when this started?

These started failing on the pfq-informational builder on Friday:

https://cros-goldeneye.corp.google.com/chromeos/healthmonitoring/buildDetails?buildbucketId=8942974985913991152

Failures appear to include:

FATAL:fontconfig_util_linux.cc(411)] Check failed: CreateTemporaryFileInDir(dir_module, &fonts_conf_file_temp).

Unfortunately, there is no longer a convenient list of chrome change sin the pfq-informational builder output. I'll file a separate bug for that...

Ah good catch. Greg was looking at SLU recently. Also, I'm kind of surprised that we're reaching fontconfig code in the sandbox unittests.

May caused by https://chromium-review.googlesource.com/c/chromium/src/+/1112179?

thomasanderson@, can you confirm?

Yes that is likely the cause.  That code should not be getting called after the sandbox is set up.  I think for now, it would probably be safe just to remove the CHECKs.

Thanks for the confirm. Since PFQ has been broken for a few days, I'll revert this CL first.

CL has been reverted at https://chromium-review.googlesource.com/c/chromium/src/+/1113840. Hopefully next PFQ run will cycle green.

The following revision refers to this bug:
  https://chromium.googlesource.com/chromium/src.git/+/81162e7432ecf59a861e5ba7be9f28b28b891dea

commit 81162e7432ecf59a861e5ba7be9f28b28b891dea
Author: Tom Anderson <thomasanderson@chromium.org>
Date: Mon Jun 25 22:44:09 2018

"Reland "Update fontconfig to 6cc99d6a"

Reason for reland: this CL includes a fallback for when the tests are run in an
installed environment.  Hopefully this should be sufficient to fix the CrOs bot
breakage.

Original change's description:
> Update fontconfig to 6cc99d6a
>
> Changelog [1].  This is necessary to pick up [2] for fixing undefined-shift
> UBSAN errors detected by clusterfuzz, [3] to allow removing a build workaround,
> [4] to fix a bug and clean up some log spam, [5] to fix CFI builds, and [6] to
> fix a use-after-free.
>
> Fontconfig also now requires libuuid as a dependency, so whitelist it as a
> dependency since we statically link fontconfig.
>
> [1] https://chromium.googlesource.com/external/fontconfig/+log/b546940435ebfb0df575bc7a2350d1e913919c34..6cc99d6a82ad67d2f5eac887b28bca13c0dfddde
> [2] https://chromium.googlesource.com/external/fontconfig/+/c60ed9ef66e59584f8b54323018e9e6c69925c7e
> [3] https://chromium.googlesource.com/external/fontconfig/+/b8a225b3c3495942480377b7b3404710c70be914
> [4] https://chromium.googlesource.com/external/fontconfig/+/7ad010e80bdf8e41303e322882ece908f5e04c74
> [5] https://chromium.googlesource.com/external/fontconfig/+/096e8019be595c2224aaabf98da630ee917ee51c
> [6] https://chromium.googlesource.com/external/fontconfig/+/6cc99d6a82ad67d2f5eac887b28bca13c0dfddde
>
> BUG= 831146 ,822737, 787020 , 829890 ,847323
> TBR=thestig,dnicoara
>
> Change-Id: Ic2d1bd19af8ca131c960a30d09246827c115ccec
> Reviewed-on: https://chromium-review.googlesource.com/1095538
> Commit-Queue: Thomas Anderson <thomasanderson@chromium.org>
> Reviewed-by: Thomas Anderson <thomasanderson@chromium.org>
> Reviewed-by: Lei Zhang <thestig@chromium.org>
> Reviewed-by: Daniel Nicoara <dnicoara@chromium.org>
> Cr-Commit-Position: refs/heads/master@{#567445}

TBR=thestig@chromium.org,dnicoara@chromium.org

Bug:  831146 , 822737,  787020 ,  829890 , 847323,  853048 ,  856142 
Change-Id: I74037fc1e7719ab61e6a5aff52ced8845482273b
Reviewed-on: https://chromium-review.googlesource.com/1114078
Reviewed-by: Thomas Anderson <thomasanderson@chromium.org>
Commit-Queue: Thomas Anderson <thomasanderson@chromium.org>
Cr-Commit-Position: refs/heads/master@{#570210}
[modify] https://crrev.com/81162e7432ecf59a861e5ba7be9f28b28b891dea/DEPS
[modify] https://crrev.com/81162e7432ecf59a861e5ba7be9f28b28b891dea/base/test/fontconfig_util_linux.cc
[modify] https://crrev.com/81162e7432ecf59a861e5ba7be9f28b28b891dea/chrome/installer/linux/debian/dist_package_versions.json
[modify] https://crrev.com/81162e7432ecf59a861e5ba7be9f28b28b891dea/chrome/installer/linux/debian/update_dist_package_versions.py
[modify] https://crrev.com/81162e7432ecf59a861e5ba7be9f28b28b891dea/chrome/installer/linux/rpm/dist_package_provides.json
[modify] https://crrev.com/81162e7432ecf59a861e5ba7be9f28b28b891dea/chrome/installer/linux/rpm/update_package_provides.py
[modify] https://crrev.com/81162e7432ecf59a861e5ba7be9f28b28b891dea/third_party/WebKit/LayoutTests/platform/linux/fast/text/unicode-fallback-font-expected.png
[modify] https://crrev.com/81162e7432ecf59a861e5ba7be9f28b28b891dea/third_party/fontconfig/BUILD.gn
[modify] https://crrev.com/81162e7432ecf59a861e5ba7be9f28b28b891dea/third_party/fontconfig/OWNERS
[modify] https://crrev.com/81162e7432ecf59a861e5ba7be9f28b28b891dea/third_party/fontconfig/README.chromium
[modify] https://crrev.com/81162e7432ecf59a861e5ba7be9f28b28b891dea/third_party/fontconfig/include/config.h
[modify] https://crrev.com/81162e7432ecf59a861e5ba7be9f28b28b891dea/third_party/fontconfig/include/fc-case/fccase.h
[modify] https://crrev.com/81162e7432ecf59a861e5ba7be9f28b28b891dea/third_party/fontconfig/include/src/fcalias.h
[modify] https://crrev.com/81162e7432ecf59a861e5ba7be9f28b28b891dea/third_party/fontconfig/include/src/fcaliastail.h
[modify] https://crrev.com/81162e7432ecf59a861e5ba7be9f28b28b891dea/third_party/fontconfig/include/src/fcftalias.h
[modify] https://crrev.com/81162e7432ecf59a861e5ba7be9f28b28b891dea/third_party/fontconfig/include/src/fcftaliastail.h
[modify] https://crrev.com/81162e7432ecf59a861e5ba7be9f28b28b891dea/third_party/fontconfig/include/src/fcobjshash.h
[modify] https://crrev.com/81162e7432ecf59a861e5ba7be9f28b28b891dea/third_party/fontconfig/include/src/fcstdint.h