Seen while testing this WebGL conformance roll (which will change the distributions of tests to shards):
https://chromium-review.googlesource.com/1225605

here:
https://ci.chromium.org/p/chromium/builders/luci.chromium.try/win_angle_rel_ng/2981

in:

webgl2_conformance_gl_passthrough_tests on Intel GPU on Windows (with patch) on Windows-10

Flakiness dashboard link:
https://test-results.appspot.com/dashboards/flakiness_dashboard.html#testType=webgl2_conformance_gl_passthrough_tests&tests=gpu_tests.webgl_conformance_integration_test.WebGLConformanceIntegrationTest.WebglConformance_conformance_uniforms_no_over_optimization_on_uniform_array_07

Swarming shard:
https://chromium-swarm.appspot.com/task?id=3fee266b8c42c010&refresh=10&show_raw=1

Log excerpt:
[98/140] gpu_tests.webgl_conformance_integration_test.WebGLConformanceIntegrationTest.WebglConformance_conformance_uniforms_no_over_optimization_on_uniform_array_07 failed unexpectedly 1.8400s:
  
  Traceback (most recent call last):
    _RunGpuTest at content\test\gpu\gpu_tests\gpu_integration_test.py:138
      self.RunActualGpuTest(url, *args)
    RunActualGpuTest at content\test\gpu\gpu_tests\webgl_conformance_integration_test.py:186
      getattr(self, test_name)(test_path, *args[1:])
    _RunConformanceTest at content\test\gpu\gpu_tests\webgl_conformance_integration_test.py:200
      self._CheckTestCompletion()
    _CheckTestCompletion at content\test\gpu\gpu_tests\webgl_conformance_integration_test.py:196
      self.fail(self._WebGLTestMessages(self.tab))
    fail at .swarming_module\bin\Lib\unittest\case.py:410
      raise self.failureException(msg)
  AssertionError: should be green
  at (0, 0) expected: 0,255,0,255 was 0,255,0,0
  FAIL should be green
  at (0, 0) expected: 0,255,0,255 was 0,255,0,0
  should be green
  at (0, 0) expected: 0,255,0,255 was 0,255,0,0
  FAIL should be green
  at (0, 0) expected: 0,255,0,255 was 0,255,0,0
 
I'm not sure what to do about this except mark the test flaky. Will do so if this shows up again.