It started failing with this build: https://build.chromium.org/p/chromium.gpu.fyi/builders/Win10%20Release%20%28Intel%20HD%20630%29/builds/881.

Here's the error log:
Traceback (most recent call last):
    _RunGpuTest at content\test\gpu\gpu_tests\gpu_integration_test.py:125
      self.RunActualGpuTest(url, *args)
    RunActualGpuTest at content\test\gpu\gpu_tests\webgl_conformance_integration_test.py:203
      getattr(self, test_name)(test_path, *args[1:])
    _RunConformanceTest at content\test\gpu\gpu_tests\webgl_conformance_integration_test.py:217
      self._CheckTestCompletion()
    _CheckTestCompletion at content\test\gpu\gpu_tests\webgl_conformance_integration_test.py:213
      self.fail(self._WebGLTestMessages(self.tab))
    fail at C:\b\depot_tools\win_tools-2_7_6_bin\python\bin\lib\unittest\case.py:412
      raise self.failureException(msg)
  AssertionError: should be green
  at (0, 0) expected: 0,255,0,255 was 255,0,0,255
  *** Error compiling VERTEX_SHADER '[object WebGLShader]':ERROR: 0:11: 'constructor' : constructor does not have any arguments
  
    *** Error compiling FRAGMENT_SHADER '[object WebGLShader]':ERROR: 0:11: 'constructor' : constructing matrix from matrix can only take one argument
  
    Locals:
    msg : u"should be green\nat (0, 0) expected: 0,255,0,255 was 255,0,0,255\n*** Error compiling VERTEX_SHADER '[object WebGLShader]':ERROR: 0:11: 'constructor' : constructor does not have any arguments\n\x00\n*** Error compiling FRAGMENT_SHADER '[object WebGLShader]':ERROR: 0:9: 'constructor' : constructor does not have any arguments\n\x00\n*** Error compiling VERTEX_SHADER '[object WebGLShader]':ERROR: 0:11: 'constructor' : not enough data provided for construction\n\x00\n*** Error compiling FRAGMENT_SHADER '[o ... TEX_SHADER '[object WebGLShader]':ERROR: 0:14: 'constructor' : constructing matrix from matrix can only take one argument\n\x00\n*** Error compiling FRAGMENT_SHADER '[object WebGLShader]':ERROR: 0:12: 'constructor' : constructing matrix from matrix can only take one argument\n\x00\n*** Error compiling VERTEX_SHADER '[object WebGLShader]':ERROR: 0:15: 'constructor' : too many arguments\n\x00\n*** Error compiling FRAGMENT_SHADER '[object WebGLShader]':ERROR: 0:13: 'constructor' : too many arguments\n\x00\n" (truncated)

Most likely its this change: https://chromium.googlesource.com/chromium/src/+/6cb6e5c0e17babc4b68a2e4a2a628beff31b64d5