James said he'd look into this.

thanks for that.

These tests are actually passing. They are getting blamed for a GPU process crash caused by a different test because the test harness doesn't detect crashes ( bug 863221 ).

The following revision refers to this bug:
  https://chromium.googlesource.com/chromium/src.git/+/d4ed2040e25c6a4bb9b8c239eabc268ede992a3f

commit d4ed2040e25c6a4bb9b8c239eabc268ede992a3f
Author: James Darpinian <jdarpinian@chromium.org>
Date: Mon Nov 05 21:56:34 2018

GPU command buffer: Support copying ALPHA/LUMINANCE on ES3

http://crrev.com/c/567306 added support for LUMINANCE, ALPHA, and
LUMINANCE_ALPHA formats to the CopyTextureCHROMIUM implementation. This
also enables that support on OpenGL ES 3 contexts for Android. Fixes
WebGL conformance tests:

conformance/textures/video/tex-2d-alpha-alpha-unsigned_byte.html
conformance/textures/video/tex-2d-luminance_alpha-luminance_alpha-unsigned_byte.html
conformance/textures/video/tex-2d-luminance-luminance-unsigned_byte.html

Bug:  878920 
Change-Id: Iee4a5189662c1c820ec2fc99b676a1b4e1beb1a0
Reviewed-on: https://chromium-review.googlesource.com/c/1302825
Commit-Queue: James Darpinian <jdarpinian@chromium.org>
Reviewed-by: Kenneth Russell <kbr@chromium.org>
Cr-Commit-Position: refs/heads/master@{#605483}
[modify] https://crrev.com/d4ed2040e25c6a4bb9b8c239eabc268ede992a3f/content/test/gpu/gpu_tests/webgl_conformance_expectations.py
[modify] https://crrev.com/d4ed2040e25c6a4bb9b8c239eabc268ede992a3f/gpu/command_buffer/service/copy_texture_chromium_mock.cc
[modify] https://crrev.com/d4ed2040e25c6a4bb9b8c239eabc268ede992a3f/gpu/command_buffer/service/copy_texture_chromium_mock.h
[modify] https://crrev.com/d4ed2040e25c6a4bb9b8c239eabc268ede992a3f/gpu/command_buffer/service/gles2_cmd_copy_tex_image.cc
[modify] https://crrev.com/d4ed2040e25c6a4bb9b8c239eabc268ede992a3f/gpu/command_buffer/service/gles2_cmd_copy_tex_image.h
[modify] https://crrev.com/d4ed2040e25c6a4bb9b8c239eabc268ede992a3f/gpu/command_buffer/service/gles2_cmd_copy_texture_chromium.cc
[modify] https://crrev.com/d4ed2040e25c6a4bb9b8c239eabc268ede992a3f/gpu/command_buffer/service/gles2_cmd_copy_texture_chromium.h
[modify] https://crrev.com/d4ed2040e25c6a4bb9b8c239eabc268ede992a3f/gpu/command_buffer/service/gles2_cmd_decoder.cc
[modify] https://crrev.com/d4ed2040e25c6a4bb9b8c239eabc268ede992a3f/gpu/command_buffer/service/gles2_cmd_decoder.h
[modify] https://crrev.com/d4ed2040e25c6a4bb9b8c239eabc268ede992a3f/gpu/command_buffer/service/gles2_cmd_decoder_mock.h
[modify] https://crrev.com/d4ed2040e25c6a4bb9b8c239eabc268ede992a3f/gpu/command_buffer/service/gles2_cmd_decoder_passthrough.cc
[modify] https://crrev.com/d4ed2040e25c6a4bb9b8c239eabc268ede992a3f/gpu/command_buffer/service/gles2_cmd_decoder_passthrough.h
[modify] https://crrev.com/d4ed2040e25c6a4bb9b8c239eabc268ede992a3f/gpu/command_buffer/service/gles2_cmd_decoder_unittest_base.cc
[modify] https://crrev.com/d4ed2040e25c6a4bb9b8c239eabc268ede992a3f/gpu/command_buffer/service/gles2_cmd_decoder_unittest_base.h
[modify] https://crrev.com/d4ed2040e25c6a4bb9b8c239eabc268ede992a3f/gpu/command_buffer/service/texture_manager.cc
[modify] https://crrev.com/d4ed2040e25c6a4bb9b8c239eabc268ede992a3f/ui/gl/gl_version_info.h

I was wrong about the tests passing. They were legitimately failing. In fixing this I ran into an ANGLE bug where swizzling cubemaps doesn't work on DX11, angleproject:2774. Luckily we don't need to emulate ALPHA/LUMINANCE on ANGLE so it's not a problem.

Great work James fixing this! Turning around the blocked on / blocking relationship to the ANGLE bug.