yunchao.he@intel.com@, could you link to the failing bot run and add the failure log here.

This is passing on my machine.

68.0.3432.3 (Official Build) dev (64-bit)
--use-gl=angle --use-cmd-decoder=passthrough
VENDOR = 0x10de, DEVICE= 0x13bb *ACTIVE*

Deleted: about-gpu.txt 15.1 KB

about-gpu.txt 15.1 KB View Download

Kai, the test failed on Chromium Linux NV bots many times. For example: https://ci.chromium.org/p/chromium/builders/luci.chromium.try/linux_angle_rel_ng/1103 and https://ci.chromium.org/p/chromium/builders/luci.chromium.try/linux_angle_rel_ng/1121 and https://ci.chromium.org/p/chromium/builders/luci.chromium.try/linux_angle_rel_ng/1127.

Sorry - not trying to imply that it wasn't a persistent issue.
Just providing a bit of extra data to try to narrow down the issue (e.g. is it device-specific or driver specific?) I haven't looked into the problem at all.

Failure log from build 1103:

[73/135] gpu_tests.webgl_conformance_integration_test.WebGLConformanceIntegrationTest.WebglConformance_conformance_misc_webgl_specific_stencil_settings failed unexpectedly 6.0691s:
  
  Traceback (most recent call last):
    _RunGpuTest at content/test/gpu/gpu_tests/gpu_integration_test.py:132
      self.RunActualGpuTest(url, *args)
    RunActualGpuTest at content/test/gpu/gpu_tests/webgl_conformance_integration_test.py:188
      getattr(self, test_name)(test_path, *args[1:])
    _RunConformanceTest at content/test/gpu/gpu_tests/webgl_conformance_integration_test.py:202
      self._CheckTestCompletion()
    _CheckTestCompletion at content/test/gpu/gpu_tests/webgl_conformance_integration_test.py:198
      self.fail(self._WebGLTestMessages(self.tab))
    fail at .swarming_module/lib/python2.7/unittest/case.py:410
      raise self.failureException(msg)
  AssertionError: gl.checkFramebufferStatus(gl.FRAMEBUFFER) should be 36054. Was 36053.
  FAIL gl.checkFramebufferStatus(gl.FRAMEBUFFER) should be 36054. Was 36053.
  getError expected: INVALID_FRAMEBUFFER_OPERATION. Was NO_ERROR : after evaluating: wtu.dummySetProgramAndDrawNothing(gl)
  FAIL getError expected: INVALID_FRAMEBUFFER_OPERATION. Was NO_ERROR : after evaluating: wtu.dummySetProgramAndDrawNothing(gl)
  getError expected: INVALID_OPERATION. Was NO_ERROR : after evaluating: wtu.dummySetProgramAndDrawNothing(gl)
  FAIL getError expected: INVALID_OPERATION. Was NO_ERROR : after evaluating: wtu.dummySetProgramAndDrawNothing(gl)

Hm, linux_angle_rel_ng seems to have stopped seeing this issue. However I can't find any hints about why this would have changed. Here's the range between a failing run and a passing run, according to the ANGLE version numbers from the swarming logs:
https://chromium.googlesource.com/angle/angle/+log/cc12937..c61a24d/
(The blamelist for build 1128 only shows one commit... and got_angle_revision shows an empty range 4607148..4607148)

The following revision refers to this bug:
  https://chromium.googlesource.com/chromium/src.git/+/f5ab530969f2873f35dbacb496da4eaf8ac8f4b5

commit f5ab530969f2873f35dbacb496da4eaf8ac8f4b5
Author: Yunchao He <yunchao.he@intel.com>
Date: Sat May 26 01:08:55 2018

Roll WebGL 7c0541d..198d637

https://chromium.googlesource.com/external/khronosgroup/webgl.git/+log/7c0541d..198d637

Bug: 609883, 611943, 611945, 844311,  844308 , 844311, 844349
Cq-Include-Trybots: luci.chromium.try:win_optional_gpu_tests_rel;luci.chromium.try:mac_optional_gpu_tests_rel;luci.chromium.try:linux_optional_gpu_tests_rel;luci.chromium.try:android_optional_gpu_tests_rel;luci.chromium.try:linux_angle_rel_ng;luci.chromium.try:win_angle_rel_ng
Change-Id: I0bd4d7409796861e6a4d73c2afc3b054d61a5a2b
Reviewed-on: https://chromium-review.googlesource.com/1063564
Reviewed-by: Kenneth Russell <kbr@chromium.org>
Commit-Queue: Kenneth Russell <kbr@chromium.org>
Cr-Commit-Position: refs/heads/master@{#562091}
[modify] https://crrev.com/f5ab530969f2873f35dbacb496da4eaf8ac8f4b5/DEPS
[modify] https://crrev.com/f5ab530969f2873f35dbacb496da4eaf8ac8f4b5/content/test/gpu/gpu_tests/webgl2_conformance_expectations.py
[modify] https://crrev.com/f5ab530969f2873f35dbacb496da4eaf8ac8f4b5/content/test/gpu/gpu_tests/webgl_conformance_expectations.py
[modify] https://crrev.com/f5ab530969f2873f35dbacb496da4eaf8ac8f4b5/content/test/gpu/gpu_tests/webgl_conformance_revision.txt