Possibly https://chromium-review.googlesource.com/c/chromium/src/+/1131634 ?

Yes, it's probably due to the recent rebaselining.

Here are the failing images, from the logs of that run:
http://chromium-browser-gpu-tests.commondatastorage.googleapis.com/view_test_results.html?2e73888372b983f4b276e95c66ff96e3d3584a72_Android_FYI_Release_Nexus_5__telemetry

I can't see any obvious difference.

Stephen, could you suppress this failure? Something like:

    self.Fail('Pixel_WebGLGreenTriangle_NoAA_Alpha',
        ['android', ('qualcomm', 'Adreno (TM) 330')], bug= 870023 )
    self.Fail('Pixel_WebGLGreenTriangle_NoAA_NoAlpha',
        ['android', ('qualcomm', 'Adreno (TM) 330')], bug= 870023 )

in src/content/test/gpu/gpu_tests/pixel_expectations.py. Please feel free to Tbr: to me. Thanks.

The following revision refers to this bug:
  https://chromium.googlesource.com/chromium/src.git/+/918e6c2ed8b1fbac6af8e38f9e0a505ed8060eb7

commit 918e6c2ed8b1fbac6af8e38f9e0a505ed8060eb7
Author: Stephen White <senorblanco@chromium.org>
Date: Thu Aug 02 16:56:14 2018

Add suppression for pixel test failure on Nexus5.

Suppress failures for

gpu_tests.pixel_integration_test.PixelIntegrationTest.Pixel_WebGLGreenTriangle_NoAA_Alpha
gpu_tests.pixel_integration_test.PixelIntegrationTest.Pixel_WebGLGreenTriangle_NoAA_NoAlpha

on Android FYI Release (Nexus 5).

Bug:  870023 
TBR: kbr@chromium.org
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
Change-Id: I6de26ae7b418a54bafd9ecc8059a51e125b021f2
Reviewed-on: https://chromium-review.googlesource.com/1160596
Commit-Queue: Stephen White <senorblanco@chromium.org>
Reviewed-by: Kenneth Russell <kbr@chromium.org>
Reviewed-by: Stephen White <senorblanco@chromium.org>
Cr-Commit-Position: refs/heads/master@{#580216}
[modify] https://crrev.com/918e6c2ed8b1fbac6af8e38f9e0a505ed8060eb7/content/test/gpu/gpu_tests/pixel_expectations.py

I'm not sure why this is failing after turning on the flag, and it looks no difference from the reference image. Could this be an rebaseline error?

-Hotlist-PixelWrangler because the failures have been suppressed, please re-add if needed.

This doesn't fail again after the flag re-enable. I'm going mark it as closed.