The test is failing on https://build.chromium.org/p/chromium.gpu.fyi/builders/Win7%20Release%20%28AMD%20R7%20240%29 and started with the following build:

https://build.chromium.org/p/chromium.gpu.fyi/builders/Win7%20Release%20%28AMD%20R7%20240%29/builds/980

And https://build.chromium.org/p/chromium.gpu.fyi/builders/Win10%20Release%20%28NVIDIA%20Quadro%20P400%29/builds/983 starting with build:
https://build.chromium.org/p/chromium.gpu.fyi/builders/Win10%20Release%20%28NVIDIA%20Quadro%20P400%29/builds/983

Here is the stack trace:

[826/2670] gpu_tests.webgl_conformance_integration_test.WebGLConformanceIntegrationTest.WebglConformance_conformance2_textures_misc_compressed_tex_from_pbo_crash passed 0.0590s
[827/2670] gpu_tests.webgl_conformance_integration_test.WebGLConformanceIntegrationTest.WebglConformance_conformance2_textures_misc_copy_texture_cube_map_AMD_bug passed 0.0770s
[4644:680:0620/135015.685:ERROR:gles2_cmd_decoder.cc(14314)] [.Offscreen-For-WebGL-06ABB2E0]GL ERROR :GL_INVALID_OPERATION : glCopyTexImage2D: incompatible color component sizes
[4644:680:0620/135015.686:ERROR:gles2_cmd_decoder.cc(14314)] [.Offscreen-For-WebGL-06ABB2E0]GL ERROR :GL_INVALID_OPERATION : glCopyTexImage2D: incompatible color component sizes
[4644:680:0620/135015.688:ERROR:gles2_cmd_decoder.cc(14314)] [.Offscreen-For-WebGL-06ABB2E0]GL ERROR :GL_INVALID_OPERATION : glCopyTexImage2D: incompatible color component sizes
[4644:680:0620/135015.698:ERROR:gles2_cmd_decoder.cc(14314)] [.Offscreen-For-WebGL-06ABB2E0]GL ERROR :GL_INVALID_OPERATION : glCopyTexImage2D: incompatible color component sizes
[4644:680:0620/135015.704:ERROR:gles2_cmd_decoder.cc(14314)] [.Offscreen-For-WebGL-06ABB2E0]GL ERROR :GL_INVALID_OPERATION : glCopyTexImage2D: incompatible color component sizes

https://chromium-review.googlesource.com/c/538082/ looks like the most likely one in that range.

Since geofflang@ likely won't be able to address this today, I'm going to revert the patch to see if it fixes the issue.