intermittent failure on https://ci.chromium.org/p/chromium/builders/luci.chromium.ci/Mac%20FYI%20Debug%20(Intel): 

it's failed twice in 50 builds.

WebglConformance_conformance_textures_misc_canvas_teximage_after_multiple_drawimages fail on Mac FYI Intel Debug

[315/466] gpu_tests.webgl_conformance_integration_test.WebGLConformanceIntegrationTest.WebglConformance_conformance_textures_misc_canvas_teximage_after_multiple_drawimages failed unexpectedly 3.8588s:
  
  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: Uncaught TypeError: Cannot read property 'firstChild' of null
  
  Locals:
    msg : u"Uncaught TypeError: Cannot read property 'firstChild' of null\n"
  
  Found crashpad_database_util
  No minidump found via crashpad_database_util
  Restarting browser due to unexpected test failure
  Closing browser (pid=13794) ...
  Browser is closed.
  Chrome Env: {'VERSIONER_PYTHON_PREFER_32_BIT': 'no', 'MAC_CHROMIUM_TMPDIR': '/b/s/w/it9Lxwp2', 'GTEST_TOTAL_SHARDS': '2', 'LOGNAME': 'chrome-bot', 'USER': 'chrome-bot', 'HOME': '/Users/chrome-bot', 'BOTO_CONFIG': '/Users/chrome-bot/.boto', 'PATH': '/b/s/w/ir/.swarming_module_cache/vpython/f1b01b/bin:/b/s/w/ir/.swarming_module:/b/s/w/ir/.swarming_module/bin:/b/s/cipd_cache/bin:/opt/local/bin:/opt/local/sbin:/usr/local/sbin:/usr/local/git/bin:/usr/local/bin:/usr/sbin:/usr/bin:/sbin:/bin:/b/s/w/ir/.swarming_module_cache/vpython/f1b01b/lib/python2.7/site-packages/cv2', 'SWARMING_BOT_ID': 'build628-m4', 'LANG': 'en_US.UTF-8', 'VIRTUAL_ENV': '/b/s/w/ir/.swarming_module_cache/vpython/f1b01b', 'Apple_PubSub_Socket_Render': '/private/tmp/com.apple.launchd.WXAu5iEHus/Render', 'SWARMING_SERVER': 'https://chromium-swarm.appspot.com', 'VERSIONER_PYTHON_VERSION': '2.7', 'CHROME_DEVEL_SANDBOX': '/opt/chromium/chrome_sandbox', 'XPC_FLAGS': '0x0', 'SWARMING_HEADLESS': '1', 'PYTHONNOUSERSITE': '1', 'LUCI_CONTEXT': '/b/s/w/it9Lxwp2/luci_ctx.9xGo3C.json', 'CIPD_CACHE_DIR': '/b/s/cipd_cache/cache', 'XPC_SERVICE_NAME': 'org.swarm.bot.plist', 'PYTHONPATH': '/b/s/w/ir/third_party/catapult/telemetry', 'SSH_AUTH_SOCK': '/private/tmp/com.apple.launchd.AfjOnvBO4A/Listeners', 'GTEST_SHARD_INDEX': '1', 'VPYTHON_VIRTUALENV_ROOT': '/b/s/w/ir/.swarming_module_cache/vpython', 'SWARMING_TASK_ID': '4130ab8a36d05111', 'SHELL': '/bin/bash', 'NO_GCE_CHECK': 'False', 'CHROME_HEADLESS': '1', 'LC_ALL': 'en_US.UTF-8', 'TMPDIR': '/b/s/w/it9Lxwp2', 'LC_MESSAGES': 'en_US.UTF-8', 'CIPD_PROTOCOL': 'v2', '__CF_USER_TEXT_ENCODING': '0x1F4:0x0:0x0', 'BREAKPAD_DUMP_LOCATION': '/b/s/w/it9Lxwp2/tmplOELKA'}
  Starting Chrome ['/b/s/w/ir/out/Debug/Chromium.app/Contents/MacOS/Chromium', '--disable-gpu-watchdog', '--enable-experimental-web-platform-features', '--test-type=gpu', '--disable-gpu-process-for-dx12-vulkan-info-collection', '--disable-domain-blocking-for-3d-apis', '--disable-gpu-process-crash-limit', '--disable-blink-features=WebXR', '--js-flags=--expose-gc', '--enable-logging=stderr', '--autoplay-policy=no-user-gesture-required', '--disable-features=UseSurfaceLayerForVideo', '--enable-net-benchmarking', '--metrics-recording-only', '--no-default-browser-check', '--no-first-run', '--ignore-background-tasks', '--enable-gpu-benchmarking', '--deny-permission-prompts', '--autoplay-policy=no-user-gesture-required', '--disable-background-networking', '--disable-component-extensions-with-background-pages', '--disable-default-apps', '--disable-search-geolocation-disclosure', '--proxy-server=socks://localhost:65506', '--proxy-bypass-list=<-loopback>', '--remote-debugging-port=0', '--enable-crash-reporter-for-testing', '--disable-component-update', '--window-size=1280,1024', '--user-data-dir=/b/s/w/it9Lxwp2/tmprcyRJa', 'about:blank']
  DoNothingForwarder started between 127.0.0.1:49854 and 49854
  Browser started (pid=13821).
  OS: mac sierra
  Detailed OS version: 10.12.6 16G29
  Model: Macmini 7.1
  Browser command line: /b/s/w/ir/out/Debug/Chromium.app/Contents/MacOS/Chromium --disable-gpu-watchdog --enable-experimental-web-platform-features --test-type=gpu --disable-gpu-process-for-dx12-vulkan-info-collection --disable-domain-blocking-for-3d-apis --disable-gpu-process-crash-limit --disable-blink-features=WebXR --js-flags=--expose-gc --enable-logging=stderr --autoplay-policy=no-user-gesture-required --disable-features=UseSurfaceLayerForVideo --enable-net-benchmarking --metrics-recording-only --no-default-browser-check --no-first-run --ignore-background-tasks --enable-gpu-benchmarking --deny-permission-prompts --autoplay-policy=no-user-gesture-required --disable-background-networking --disable-component-extensions-with-background-pages --disable-default-apps --disable-search-geolocation-disclosure --proxy-server=socks://localhost:65506 --proxy-bypass-list=<-loopback> --remote-debugging-port=0 --enable-crash-reporter-for-testing --disable-component-update --window-size=1280,1024 --user-data-dir=/b/s/w/it9Lxwp2/tmprcyRJa --flag-switches-begin --flag-switches-end about:blank
  GPU device 0: VENDOR = 0x8086 (Intel Inc.), DEVICE = 0xa2e (Intel Iris OpenGL Engine)
  GPU Attributes:
    amd_switchable      : False
    can_support_threaded_texture_mailbox: False
    direct_rendering    : True
    encrypted_only      : False
    gl_extensions       : GL_ARB_blend_func_extended GL_ARB_draw_buffers_blend GL_ARB_draw_indirect GL_ARB_ES2_compatibility GL_ARB_explicit_attrib_location GL_ARB_gpu_shader_fp64 GL_ARB_gpu_shader5 GL_ARB_instanced_arrays GL_ARB_internalformat_query GL_ARB_occlusion_query2 GL_ARB_sample_shading GL_ARB_sampler_objects GL_ARB_separate_shader_objects GL_ARB_shader_bit_encoding GL_ARB_shader_subroutine GL_ARB_shading_language_include GL_ARB_tessellation_shader GL_ARB_texture_buffer_object_rgb32 GL_ARB_texture_cube_map_array GL_ARB_texture_gather GL_ARB_texture_query_lod GL_ARB_texture_rgb10_a2ui GL_ARB_texture_storage GL_ARB_texture_swizzle GL_ARB_timer_query GL_ARB_transform_feedback2 GL_ARB_transform_feedback3 GL_ARB_vertex_attrib_64bit GL_ARB_vertex_type_2_10_10_10_rev GL_ARB_viewport_array GL_EXT_debug_label GL_EXT_debug_marker GL_EXT_framebuffer_multisample_blit_scaled GL_EXT_texture_compression_s3tc GL_EXT_texture_filter_anisotropic GL_EXT_texture_sRGB_decode GL_APPLE_client_storage GL_APPLE_container_object_shareable GL_APPLE_flush_render GL_APPLE_object_purgeable GL_APPLE_rgb_422 GL_APPLE_row_bytes GL_APPLE_texture_range GL_ATI_texture_mirror_once GL_NV_texture_barrier
    gl_renderer         : Intel Iris OpenGL Engine
    gl_reset_notification_strategy: 0
    gl_vendor           : Intel Inc.
    gl_version          : 4.1 INTEL-10.25.17
    gl_ws_extensions    : 
    gl_ws_vendor        : 
    gl_ws_version       : 
    in_process_gpu      : False
    initialization_time : 0.094436
    jpeg_decode_accelerator_supported: False
    max_framerate_denominator: 1
    max_framerate_numerator: 30
    max_msaa_samples    : 8
    max_resolution_height: 2160
    max_resolution_width: 4096
    min_resolution_height: 16
    min_resolution_width: 16
    oop_rasterization_supported: True
    optimus             : False
    passthrough_cmd_decoder: False
    pixel_shader_version: 4.10
    process_crash_count : 0
    profile             : 3
    sandboxed           : True
    software_rendering  : False
    vertex_shader_version: 4.10
    video_decode_accelerator_flags: 0
  Feature Status:
    2d_canvas           : enabled
    flash_3d            : enabled
    flash_stage3d       : enabled
    flash_stage3d_baseline: enabled
    gpu_compositing     : enabled
    multiple_raster_threads: enabled_on
    native_gpu_memory_buffers: enabled
    oop_rasterization   : enabled
    protected_video_decode: unavailable_off
    rasterization       : enabled
    skia_deferred_display_list: disabled_off
    skia_renderer       : disabled_off
    surface_control     : disabled_off
    surface_synchronization: enabled_on
    video_decode        : enabled
    viz_display_compositor: enabled_on
    webgl               : enabled
    webgl2              : enabled
  Driver Bug Workarounds:
    add_and_true_to_loop_condition
    adjust_src_dst_region_for_blitframebuffer
    avoid_stencil_buffers
    decode_encode_srgb_for_generatemipmap
    disable_2d_canvas_auto_flush
    disable_framebuffer_cmaa
    disable_webgl_rgb_multisampling_usage
    dont_use_loops_to_initialize_variables
    emulate_abs_int_function
    get_frag_data_info_bug
    init_two_cube_map_levels_before_copyteximage
    max_msaa_sample_count_4
    msaa_is_slow
    pack_parameters_workaround_with_pack_buffer
    rebind_transform_feedback_before_resume
    regenerate_struct_names
    remove_invariant_and_centroid_for_essl3
    reset_teximage2d_base_level
    rewrite_texelfetchoffset_to_texelfetch
    scalarize_vec_and_mat_constructor_args
    set_zero_level_before_generating_mipmap
    unfold_short_circuit_as_ternary_operation
    unpack_alignment_workaround_with_unpack_buffer
    unpack_image_height_workaround_with_unpack_buffer
    use_intermediary_for_copy_texture_image
    use_unused_standard_shared_blocks
    disabled_extension__gl__khr_blend_equation_advanced
    disabled_extension__gl__khr_blend_equation_advanced_coherent
  Traceback (most recent call last):
    File "/b/s/w/ir/third_party/catapult/telemetry/telemetry/testing/serially_executed_browser_test_case.py", line 214, in <lambda>
      return lambda self: based_method(self, *args)
    File "/b/s/w/ir/content/test/gpu/gpu_tests/gpu_integration_test.py", line 155, in _RunGpuTest
      self.RunActualGpuTest(url, *args)
    File "/b/s/w/ir/content/test/gpu/gpu_tests/webgl_conformance_integration_test.py", line 190, in RunActualGpuTest
      getattr(self, test_name)(test_path, *args[1:])
    File "/b/s/w/ir/content/test/gpu/gpu_tests/webgl_conformance_integration_test.py", line 210, in _RunConformanceTest
      self._CheckTestCompletion()
    File "/b/s/w/ir/content/test/gpu/gpu_tests/webgl_conformance_integration_test.py", line 206, in _CheckTestCompletion
      self.fail(self._WebGLTestMessages(self.tab))
  AssertionError: Uncaught TypeError: Cannot read property 'firstChild' of null
  
[13821:775:1115/065854.269045:INFO:CONSOLE(1)] "WebGL: INVALID_ENUM: compressedTexSubImage2D: invalid format", source:  (1)
[13821:775:1115/065854.275539:INFO:CONSOLE(1)] "WebGL: INVALID_ENUM: compressedTexImage2D: invalid format", source:  (1)
[13821:775:1115/065854.277150:INFO:CONSOLE(1)] "WebGL: INVALID_ENUM: compressedTexImage2D: invalid format", source:  (1)
[13821:775:1115/065854.282058:INFO:CONSOLE(1)] "WebGL: INVALID_ENUM: compressedTexSubImage2D: invalid format", source:  (1)
[13821:775:1115/065854.284961:INFO:CONSOLE(78)] "WebGL: INVALID_ENUM: compressedTexImage2D: invalid format", source: http://127.0.0.1:65522/third_party/webgl/src/sdk/tests/conformance/textures/misc/compressed-tex-image.html (78)
[13821:775:1115/065854.291602:INFO:CONSOLE(85)] "WebGL: INVALID_ENUM: compressedTexSubImage2D: invalid format", source: http://127.0.0.1:65522/third_party/webgl/src/sdk/tests/conformance/textures/misc/compressed-tex-image.html (85)
DevTools console [network]: Failed to load resource: the server responded with a status of 404 (File not found) http://127.0.0.1:65522/favicon.ico