Hm, the tests are running with --no-xvfb ... do you know if they run in a real X11 session?

Yes, they do on these machines.

They also do on the linux_chromium_rel_ng tryserver. See:
https://ci.chromium.org/buildbot/tryserver.chromium.linux/linux_chromium_rel_ng/576203

The step "gl_unittests on NVIDIA GPU on Linux (with patch) on Ubuntu" is green in your trybot run. Not sure why they're failing on AMD and Intel GPUs.

I have some workarounds I would like to try. It doesn't look like there are trybots for intel/amd though?

https://chromium-review.googlesource.com/c/chromium/src/+/747523 is the change I was going to try.

If that doesn't work, then a while (XNextEvent()) loop until we receive a WM_DELETE_WINDOW event after XDestroyWindow() before making the call to MakeCurrent(). But I am not sure how I can test. Do you have advice?

Sorry, that's true, there are currently no trybots for Linux Intel or AMD. It's possible to log on to the bots using the GPU pixel wrangling instructions in a pinch though. We are working on building out Linux Intel capacity and tryservers in coming quarters.

I LGTM'd https://chromium-review.googlesource.com/c/chromium/src/+/747523 . Let's get it in now to try to get some testing in.

The following revision refers to this bug:
  https://chromium.googlesource.com/chromium/src.git/+/d99931419391773504b4958dbd8512ee7d1852c1

commit d99931419391773504b4958dbd8512ee7d1852c1
Author: Sadrul Habib Chowdhury <sadrul@chromium.org>
Date: Tue Oct 31 22:28:49 2017

glx: Turn off XSynchronize at the end of the test.

BUG= 780118 

Cq-Include-Trybots: master.tryserver.chromium.android:android_optional_gpu_tests_rel;master.tryserver.chromium.linux:linux_optional_gpu_tests_rel;master.tryserver.chromium.mac:mac_optional_gpu_tests_rel;master.tryserver.chromium.win:win_optional_gpu_tests_rel
Change-Id: I58ae9e17241637331c4e0ae47fb3eeaac9761342
Reviewed-on: https://chromium-review.googlesource.com/747523
Reviewed-by: Kenneth Russell <kbr@chromium.org>
Commit-Queue: Sadrul Chowdhury <sadrul@chromium.org>
Cr-Commit-Position: refs/heads/master@{#512979}
[modify] https://crrev.com/d99931419391773504b4958dbd8512ee7d1852c1/ui/gl/gl_context_glx_unittest.cc

Doesn't seem to have helped? :-( I will put up a CL for the alternative approach in the morning.

The following revision refers to this bug:
  https://chromium.googlesource.com/chromium/src.git/+/0e57a362ce424bea4e675b455077b053e3201ade

commit 0e57a362ce424bea4e675b455077b053e3201ade
Author: Sadrul Habib Chowdhury <sadrul@chromium.org>
Date: Wed Nov 01 21:23:35 2017

glx: Disable a test.

The test is failing on intel and amd, but not on nvidia. Disable it
now while I investigate.

TBR=kbr@chromium.org
BUG= 780118 

Cq-Include-Trybots: master.tryserver.chromium.android:android_optional_gpu_tests_rel;master.tryserver.chromium.linux:linux_optional_gpu_tests_rel;master.tryserver.chromium.mac:mac_optional_gpu_tests_rel;master.tryserver.chromium.win:win_optional_gpu_tests_rel
Change-Id: Iae399d4079aefdd76facfe08df8280ede8b7327c
Reviewed-on: https://chromium-review.googlesource.com/749784
Reviewed-by: Sadrul Chowdhury <sadrul@chromium.org>
Reviewed-by: Kenneth Russell <kbr@chromium.org>
Commit-Queue: Sadrul Chowdhury <sadrul@chromium.org>
Cr-Commit-Position: refs/heads/master@{#513273}
[modify] https://crrev.com/0e57a362ce424bea4e675b455077b053e3201ade/ui/gl/gl_context_glx_unittest.cc

The following revision refers to this bug:
  https://chromium.googlesource.com/chromium/src.git/+/da2571bcff96a4400adeb08b5b86e460a1fc2abc

commit da2571bcff96a4400adeb08b5b86e460a1fc2abc
Author: Sadrul Habib Chowdhury <sadrul@chromium.org>
Date: Fri Nov 03 06:09:05 2017

glx: Change how a test works.

Instead of using XSynchronize to turn on sync behaviour on x11, wait for
the relevant X events to come in to make sure the window is created,
destroyed at the expected times.

Bug:  780118 
Cq-Include-Trybots: master.tryserver.chromium.android:android_optional_gpu_tests_rel;master.tryserver.chromium.linux:linux_optional_gpu_tests_rel;master.tryserver.chromium.mac:mac_optional_gpu_tests_rel;master.tryserver.chromium.win:win_optional_gpu_tests_rel
Change-Id: Ie6d160c0e70053a0d15fc234a12f84bed5e1e2b8
Reviewed-on: https://chromium-review.googlesource.com/749644
Commit-Queue: Sadrul Chowdhury <sadrul@chromium.org>
Reviewed-by: Antoine Labour <piman@chromium.org>
Cr-Commit-Position: refs/heads/master@{#513708}
[modify] https://crrev.com/da2571bcff96a4400adeb08b5b86e460a1fc2abc/ui/gl/gl_context_glx_unittest.cc

The following revision refers to this bug:
  https://chromium.googlesource.com/chromium/src.git/+/04e9fdeb27060fad91117d255bbdda5df2bc333a

commit 04e9fdeb27060fad91117d255bbdda5df2bc333a
Author: Sadrul Habib Chowdhury <sadrul@chromium.org>
Date: Fri Nov 03 13:58:42 2017

glx: Delete an expectation in test.

The test seems to behave differently depending on what driver is
being used. So remove an expectation for X11 failure that does not
hold on all cases.

BUG= 780118 
TBR=piman@

Cq-Include-Trybots: master.tryserver.chromium.android:android_optional_gpu_tests_rel;master.tryserver.chromium.linux:linux_optional_gpu_tests_rel;master.tryserver.chromium.mac:mac_optional_gpu_tests_rel;master.tryserver.chromium.win:win_optional_gpu_tests_rel
Change-Id: I7f3aa91883fc90e9b4da8b008b0fc6604d4f55e5
Reviewed-on: https://chromium-review.googlesource.com/753701
Commit-Queue: Sadrul Chowdhury <sadrul@chromium.org>
Reviewed-by: Sadrul Chowdhury <sadrul@chromium.org>
Cr-Commit-Position: refs/heads/master@{#513764}
[modify] https://crrev.com/04e9fdeb27060fad91117d255bbdda5df2bc333a/ui/gl/gl_context_glx_unittest.cc

Thanks for following up on this!