first failures:

webgl2_conformance_tests on ATI GPU on Mac on Mac-10.12 Run on OS: 'Mac-10.12'
https://ci.chromium.org/p/chromium/builders/luci.chromium.ci/Mac%20Pro%20FYI%20Release%20%28AMD%29/3377

webgl2_conformance_gl_passthrough_tests on Intel GPU on Linux on Ubuntu Run on OS: 'Ubuntu'
https://ci.chromium.org/p/chromium/builders/luci.chromium.ci/Linux%20FYI%20Release%20%28Intel%20HD%20630%29/7344

webgl2_conformance_tests on ATI GPU on Linux on Ubuntu Run on OS: 'Ubuntu'
https://ci.chromium.org/p/chromium/builders/luci.chromium.ci/Linux%20FYI%20Release%20%28AMD%20R7%20240%29/2356

Seems not to be an ANGLE bug - ANGLE revision did not change in any of the above.

My guess is:
https://chromium-review.googlesource.com/c/1352494


[42/141] gpu_tests.webgl_conformance_integration_test.WebGLConformanceIntegrationTest.WebglConformance_conformance2_textures_misc_tex_mipmap_levels failed unexpectedly 1.2210s:
  
  Traceback (most recent call last):
    _RunGpuTest at content/test/gpu/gpu_tests/gpu_integration_test.py:155
      self.RunActualGpuTest(url, *args)
    RunActualGpuTest at content/test/gpu/gpu_tests/webgl_conformance_integration_test.py:190
      getattr(self, test_name)(test_path, *args[1:])
    _RunConformanceTest at content/test/gpu/gpu_tests/webgl_conformance_integration_test.py:210
      self._CheckTestCompletion()
    _CheckTestCompletion at content/test/gpu/gpu_tests/webgl_conformance_integration_test.py:206
      self.fail(self._WebGLTestMessages(self.tab))
    fail at .swarming_module/lib/python2.7/unittest/case.py:410
      raise self.failureException(msg)
  AssertionError: should draw with [255, 0, 0, 255]
  at (0, 0) expected: 255,0,0,255 was 0,0,0,255
  FAIL should draw with [255, 0, 0, 255]
  at (0, 0) expected: 255,0,0,255 was 0,0,0,255
  
  Locals:
    msg : u'should draw with [255, 0, 0, 255]\nat (0, 0) expected: 255,0,0,255 was 0,0,0,255\nFAIL should draw with [255, 0, 0, 255]\nat (0, 0) expected: 255,0,0,255 was 0,0,0,255\n'