I just got a random [FATAL:channel_win.cc(292)] Check failed: reject_writes_ in 
https://logs.chromium.org/v/?s=chromium%2Fbb%2Ftryserver.chromium.win%2Fwin7_chromium_rel_ng%2F137330%2F%2B%2Frecipes%2Fsteps%2Fbrowser_tests__with_patch_%2F0%2Fstdout for the test CrExtensionsErrorConsoleA11yTest.ErrorConsole_aria_valid_attr 

This has also happened for TwoClientAppsSyncTest.StartWithDifferentApps and that test was eventually disabled because it was not stable. (See  bug 434438 ) so it seems it might be a system rather than a test problem.

The full stack in this case (don't think it's helpful):

[ RUN      ] CrExtensionsErrorConsoleA11yTest.ErrorConsole_aria_valid_attr
[10140:2000:0404/120118.361:WARNING:discovery_network_list_win.cc(195)] Failed to open Wlan client handle: 1062
[10140:8652:0404/120118.366:WARNING:chrome_browser_main_win.cc(630)] Command line too long for RegisterApplicationRestart:  --brave-new-test-launcher --cfi-diag=0 --gtest_also_run_disabled_tests --gtest_filter=CrExtensionsErrorConsoleA11yTest.ErrorConsole_aria_valid_attr --single_process --test-launcher-bot-mode --test-launcher-output="C:\Users\CHROME~2\AppData\Local\Temp\scoped_dir6460_10940\results6460_27115\test_results.xml" --test-launcher-summary-output="e:\b\swarm_slave\w\iojy6rka\output.json" --user-data-dir="C:\Users\CHROME~2\AppData\Local\Temp\scoped_dir6460_10940\d6460_32409" --disable-offline-auto-reload --enable-blink-features=MojoJSTest --no-first-run --no-default-browser-check --enable-logging=stderr --disable-default-apps --wm-window-animations-disabled --disable-component-update --test-type=browser --force-color-profile=srgb --disable-zero-browsers-open-for-tests --ipc-connection-timeout=30 --allow-file-access-from-files --dom-automation --log-gpu-control-list-decisions --disable-backgrounding-occluded-windows --disable-gl-drawing-for-tests --override-use-software-gl-for-tests --force-color-profile=srgb --disable-compositor-ukm-for-tests --enable-features=MaterialDesignExtensions,TestFeatureForBrowserTest1 --disable-features=NetworkPrediction,TestFeatureForBrowserTest2 --flag-switches-begin --flag-switches-end --restore-last-session about:blank
[5700:8708:0404/120118.528:INFO:media_foundation_video_encode_accelerator_win.cc(370)] Windows versions earlier than 8 are not supported.
[10140:8652:0404/120118.554:WARNING:gaia_auth_fetcher.cc(873)] Could not reach Google Accounts servers: errno -11
[10140:8652:0404/120119.065:INFO:CONSOLE(5)] "line1", source: chrome-extension://pdlpifnclfacjobnmbpngemkalkjamnf/script.js (5)
[10140:8652:0404/120119.066:INFO:CONSOLE(6)] "line2", source: chrome-extension://pdlpifnclfacjobnmbpngemkalkjamnf/script.js (6)
[10140:8652:0404/120119.380:INFO:CONSOLE(6)] "Boom!", source: chrome-extension://oehidglfoeondlkoeloailjdmmghacge/code.js (6)
[10140:8652:0404/120119.455:WARNING:gaia_auth_fetcher.cc(873)] Could not reach Google Accounts servers: errno -11
[10140:8652:0404/120121.204:INFO:CONSOLE(1225)] "Running TestCase CrExtensionsErrorConsoleA11yTest.ErrorConsole_aria_valid_attr", source: file:///E:/b/swarm_slave/w/ir/chrome/test/data/webui/test_api.js (1225)
[10140:8652:0404/120122.039:WARNING:gaia_auth_fetcher.cc(873)] Could not reach Google Accounts servers: errno -11
[10140:9716:0404/120122.185:FATAL:channel_win.cc(292)] Check failed: reject_writes_. 
Backtrace:
	base::debug::StackTrace::StackTrace [0x035F8480+32]
	base::debug::StackTrace::StackTrace [0x035BDEDD+13]
	logging::LogMessage::~LogMessage [0x03565273+83]
	base::circular_deque<std::unique_ptr<mojo::edk::Channel::Message,std::default_delete<mojo::edk::Channel::Message> > >::emplace_back<std::unique_ptr<mojo::edk::Channel::Message,std::default_delete<mojo::edk::Channel::Message> > > [0x0215593A+240]
	mojo::edk::Channel::Create [0x021553A5+2909]
	base::MessagePumpForIO::WaitForIOCompletion [0x035D8250+336]
	base::MessagePumpForIO::DoRunLoop [0x035D809B+59]
	base::MessagePumpWin::Run [0x035D73AE+110]
	base::MessageLoop::Run [0x03599119+169]
	base::RunLoop::Run [0x03573CFC+204]
	base::Thread::Run [0x035B1B94+164]
	content::BrowserProcessSubThread::IOThreadRun [0x0236B064+36]
	content::BrowserProcessSubThread::Run [0x0236AFE8+168]
	base::Thread::ThreadMain [0x035B1E27+631]
	base::PlatformThread::GetCurrentThreadPriority [0x0358F385+469]
	BaseThreadInitThunk [0x751B337A+18]
	RtlInitializeExceptionChain [0x773192B2+99]
	RtlInitializeExceptionChain [0x77319285+54]
[516/806] CrExtensionsErrorConsoleA11yTest.ErrorConsole_aria_valid_attr (CRASHED)