This might cause two Win GPU bots to turn purple:

https://build.chromium.org/p/chromium.gpu.fyi/builders/Win10%20Release%20%28NVIDIA%29

https://build.chromium.org/p/chromium.gpu.fyi/builders/Win10%20Debug%20%28NVIDIA%29

The symptoms are the same: shards run to the end successfully, but the step to consolidate stdout from shards failed with an exception

I do agree the spurious errors are annoying. The LogGLDebugMessage could be spammy, but it only applies to the gl back-end, so I don't know if it would be causing the step webgl2_conformance_tests on the d3d11 back-end to fail (the default on Windows 10).

The second message is also annoying but should only happen once per start-up. It's coming from a compositor shader somewhere. It's been present for many months so I would be surprised if that's causing an issue now.

I'm going to say it's pretty unlikely these particular messages are causing the purple tests.

The debug bot does fail on webgl_conformance_gl_tests, so hopefully geofflang's CL will fix that.

I agree with you the Win Release NVidia bot might be something else, although it happens to turn purple around the same time as the debug bot, so that looks suspicious.

Closing this, it's no longer an issue.

The following revision refers to this bug:
  https://chromium.googlesource.com/angle/angle/+/7c37ca1836402b654dbbf5f00007e09bdf2a7051

commit 7c37ca1836402b654dbbf5f00007e09bdf2a7051
Author: Geoff Lang <geofflang@chromium.org>
Date: Tue Jun 26 16:05:44 2018

RendererGL: Limit warning output to 5 per message type.

BUG= 768943 

Change-Id: I8ed69c70d1914b56145c52ffe26f13193fb55e9e
Reviewed-on: https://chromium-review.googlesource.com/685278
Commit-Queue: Geoff Lang <geofflang@chromium.org>
Reviewed-by: Corentin Wallez <cwallez@chromium.org>

[modify] https://crrev.com/7c37ca1836402b654dbbf5f00007e09bdf2a7051/src/libANGLE/renderer/gl/RendererGL.cpp
[modify] https://crrev.com/7c37ca1836402b654dbbf5f00007e09bdf2a7051/src/libANGLE/renderer/gl/RendererGL.h
[modify] https://crrev.com/7c37ca1836402b654dbbf5f00007e09bdf2a7051/src/libANGLE/renderer/gl/renderergl_utils.cpp
[modify] https://crrev.com/7c37ca1836402b654dbbf5f00007e09bdf2a7051/src/libANGLE/renderer/gl/renderergl_utils.h

The following revision refers to this bug:
  https://chromium.googlesource.com/chromium/src.git/+/de7bef0c6f3f99a613e8143f4d4c1008fc8361cb

commit de7bef0c6f3f99a613e8143f4d4c1008fc8361cb
Author: angle-chromium-autoroll <angle-chromium-autoroll@skia-buildbots.google.com.iam.gserviceaccount.com>
Date: Tue Jun 26 18:12:24 2018

Roll src/third_party/angle a75aa3b2c314..7c37ca183640 (1 commits)

https://chromium.googlesource.com/angle/angle.git/+log/a75aa3b2c314..7c37ca183640


git log a75aa3b2c314..7c37ca183640 --date=short --no-merges --format='%ad %ae %s'
2018-06-26 geofflang@chromium.org RendererGL: Limit warning output to 5 per message type.


Created with:
  gclient setdep -r src/third_party/angle@7c37ca183640

The AutoRoll server is located here: https://angle-chromium-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:768943 
TBR=ynovikov@chromium.org

Change-Id: If59c2a30bc13fb845937e8b1e4dffca4333793ae
Reviewed-on: https://chromium-review.googlesource.com/1115198
Reviewed-by: angle-chromium-autoroll <angle-chromium-autoroll@skia-buildbots.google.com.iam.gserviceaccount.com>
Commit-Queue: angle-chromium-autoroll <angle-chromium-autoroll@skia-buildbots.google.com.iam.gserviceaccount.com>
Cr-Commit-Position: refs/heads/master@{#570465}
[modify] https://crrev.com/de7bef0c6f3f99a613e8143f4d4c1008fc8361cb/DEPS

The following revision refers to this bug:
  https://chromium.googlesource.com/angle/angle/+/3f332584e94f21b70a88de1dd64bead4847bd742

commit 3f332584e94f21b70a88de1dd64bead4847bd742
Author: Geoff Lang <geofflang@chromium.org>
Date: Tue Jun 26 21:00:29 2018

Revert "RendererGL: Limit warning output to 5 per message type."

This reverts commit 7c37ca1836402b654dbbf5f00007e09bdf2a7051.

Reason for revert: Causes crashes on Android.

Original change's description:
> RendererGL: Limit warning output to 5 per message type.
> 
> BUG= 768943 
> 
> Change-Id: I8ed69c70d1914b56145c52ffe26f13193fb55e9e
> Reviewed-on: https://chromium-review.googlesource.com/685278
> Commit-Queue: Geoff Lang <geofflang@chromium.org>
> Reviewed-by: Corentin Wallez <cwallez@chromium.org>

TBR=geofflang@chromium.org,cwallez@chromium.org

Change-Id: I641ac5d508d238e275eaeef4fac4033d9015960d
No-Presubmit: true
No-Tree-Checks: true
No-Try: true
Bug:  768943 
Reviewed-on: https://chromium-review.googlesource.com/1115658
Commit-Queue: Geoff Lang <geofflang@chromium.org>
Reviewed-by: Geoff Lang <geofflang@chromium.org>

[modify] https://crrev.com/3f332584e94f21b70a88de1dd64bead4847bd742/src/libANGLE/renderer/gl/RendererGL.cpp
[modify] https://crrev.com/3f332584e94f21b70a88de1dd64bead4847bd742/src/libANGLE/renderer/gl/RendererGL.h
[modify] https://crrev.com/3f332584e94f21b70a88de1dd64bead4847bd742/src/libANGLE/renderer/gl/renderergl_utils.cpp
[modify] https://crrev.com/3f332584e94f21b70a88de1dd64bead4847bd742/src/libANGLE/renderer/gl/renderergl_utils.h

The following revision refers to this bug:
  https://chromium.googlesource.com/angle/angle/+/e0234aeb623e600dd70380ff44a849455994863d

commit e0234aeb623e600dd70380ff44a849455994863d
Author: Geoff Lang <geofflang@chromium.org>
Date: Tue Jun 26 21:51:20 2018

GL: Don't print driver performance warnings.

They can add an large ammount of spam to the logs of our test suites and have
never been actionable.

BUG= 768943 

Change-Id: Ibee3d7ece97cc03500b10ffa7bcaf3a4d7d51581
Reviewed-on: https://chromium-review.googlesource.com/1115700
Reviewed-by: Jamie Madill <jmadill@chromium.org>
Commit-Queue: Geoff Lang <geofflang@chromium.org>

[modify] https://crrev.com/e0234aeb623e600dd70380ff44a849455994863d/src/libANGLE/renderer/gl/RendererGL.cpp

The following revision refers to this bug:
  https://chromium.googlesource.com/chromium/src.git/+/c6a8a84d43df8eb4cb856ee2ed68978cc2f3d0b3

commit c6a8a84d43df8eb4cb856ee2ed68978cc2f3d0b3
Author: angle-chromium-autoroll <angle-chromium-autoroll@skia-buildbots.google.com.iam.gserviceaccount.com>
Date: Tue Jun 26 22:58:21 2018

Roll src/third_party/angle 7c37ca183640..1ff0ee751d95 (16 commits)

https://chromium.googlesource.com/angle/angle.git/+log/7c37ca183640..1ff0ee751d95


git log 7c37ca183640..1ff0ee751d95 --date=short --no-merges --format='%ad %ae %s'
2018-06-26 ynovikov@chromium.org Skip MaxTextureSizeTest.SpecificationTexImage on Win Intel Vulkan
2018-06-26 geofflang@chromium.org Revert "RendererGL: Limit warning output to 5 per message type."
2018-06-26 fjhenigman@chromium.org Vulkan: add SCALED vertex formats to table.
2018-06-26 lucferron@chromium.org Ozone: Skip test failing just on GLES
2018-06-26 jmadill@chromium.org Vulkan: Fix unused sampler struct uniforms.
2018-06-26 jmadill@chromium.org Program: Sampler uniform query in front-end.
2018-06-26 fjhenigman@chromium.org Vulkan: enable some vertex data tests.
2018-06-26 tobine@google.com Move PlatformMethods constructor to header
2018-06-26 jmadill@chromium.org Vulkan: Remove expectations for passing/missing tests.
2018-06-26 jmadill@chromium.org Add kEmptyImmutableString.
2018-06-26 lucferron@chromium.org Vulkan: Edge case test and fix for alpha channel masks
2018-06-26 lucferron@chromium.org Context init should set DIRTY_BIT_DRAW_FRAMEBUFFER_BINDING
2018-06-26 geofflang@chromium.org Partially revert "WGL: Support unvirtualized contexts and unsafe multithreading."
2018-06-26 jmadill@chromium.org Vulkan: Implement nested sampler structs.
2018-06-26 jmadill@chromium.org Vulkan: Sampler structs in arrays.
2018-06-26 ianelliott@google.com Initial Android implementation of GetSystemInfo


Created with:
  gclient setdep -r src/third_party/angle@1ff0ee751d95

The AutoRoll server is located here: https://angle-chromium-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:768943 
TBR=ynovikov@chromium.org

Change-Id: I2596bb1253fb3d500bfc2135d816c81d92c7f51e
Reviewed-on: https://chromium-review.googlesource.com/1115739
Reviewed-by: angle-chromium-autoroll <angle-chromium-autoroll@skia-buildbots.google.com.iam.gserviceaccount.com>
Commit-Queue: angle-chromium-autoroll <angle-chromium-autoroll@skia-buildbots.google.com.iam.gserviceaccount.com>
Cr-Commit-Position: refs/heads/master@{#570567}
[modify] https://crrev.com/c6a8a84d43df8eb4cb856ee2ed68978cc2f3d0b3/DEPS

The following revision refers to this bug:
  https://chromium.googlesource.com/chromium/src.git/+/3193df36b5101ad21d2564b10bf4a409afbaa1a5

commit 3193df36b5101ad21d2564b10bf4a409afbaa1a5
Author: angle-chromium-autoroll <angle-chromium-autoroll@skia-buildbots.google.com.iam.gserviceaccount.com>
Date: Wed Jun 27 05:24:11 2018

Roll src/third_party/angle 1ff0ee751d95..82af620e0559 (3 commits)

https://chromium.googlesource.com/angle/angle.git/+log/1ff0ee751d95..82af620e0559


git log 1ff0ee751d95..82af620e0559 --date=short --no-merges --format='%ad %ae %s'
2018-06-27 jie.a.chen@intel.com ParallelCompile: Add entry points.
2018-06-26 ynovikov@chromium.org Skip ClearTest.ChangeFramebufferAttachmentFromRGBAtoRGB on Mac
2018-06-26 geofflang@chromium.org GL: Don't print driver performance warnings.


Created with:
  gclient setdep -r src/third_party/angle@82af620e0559

The AutoRoll server is located here: https://angle-chromium-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:849576, chromium:768943 
TBR=ynovikov@chromium.org

Change-Id: Icacd1c10488eb3135f5161aac00efd8da3cf4720
Reviewed-on: https://chromium-review.googlesource.com/1116083
Reviewed-by: angle-chromium-autoroll <angle-chromium-autoroll@skia-buildbots.google.com.iam.gserviceaccount.com>
Commit-Queue: angle-chromium-autoroll <angle-chromium-autoroll@skia-buildbots.google.com.iam.gserviceaccount.com>
Cr-Commit-Position: refs/heads/master@{#570666}
[modify] https://crrev.com/3193df36b5101ad21d2564b10bf4a409afbaa1a5/DEPS