Seems to affect these two tests only:

TabCaptureApiPixelTest.EndToEndThroughWebRTC
TabCaptureApiPixelTest.EndToEndWithoutRemoting

If no CL is causing the failures, please engage the infrastructure troopers to check the bot.

The tests actually pass. There's some weird problem with the at_exit handler.

CastStreamingApiTestWithPixelOutput.EndToEnd (run #1):
[ RUN      ] CastStreamingApiTestWithPixelOutput.EndToEnd
[2676:3892:0714/034724:WARNING:chrome_browser_main_win.cc(420)] Command line too long for RegisterApplicationRestart
[1476:1416:0714/034725:ERROR:singleton_hwnd.cc(34)] Cannot create windows on non-UI thread!
[3888:2444:0714/034725:ERROR:singleton_hwnd.cc(34)] Cannot create windows on non-UI thread!
[2676:1596:0714/034728:ERROR:audio_manager_win.cc(464)] GetPreferredAudioParameters failed: 88890004
[2676:1596:0714/034728:ERROR:audio_manager_win.cc(464)] GetPreferredAudioParameters failed: 88890004
[2676:1596:0714/034728:ERROR:audio_manager_win.cc(464)] GetPreferredAudioParameters failed: 88890004
[2676:1596:0714/034728:ERROR:audio_output_resampler.cc(240)] Unable to open audio device in low latency mode.  Falling back to high latency audio output.
[2676:1596:0714/034728:ERROR:audio_output_resampler.cc(250)] Unable to open audio device in high latency mode.  Falling back to fake audio output.
[2676:3892:0714/034728:INFO:CONSOLE(70)] "The provided value 'undefined' is not a valid enum value of type OscillatorType.", source: chrome-extension://ddchlicdkolnonkihahngkmmmjnjlkkf/end_to_end_sender.js (70)
[2676:3892:0714/034728:INFO:CONSOLE(0)] "[SUCCESS] sendTestPatterns", source: chrome-extension://ddchlicdkolnonkihahngkmmmjnjlkkf/end_to_end_sender.html?port=53855&aesKey=30313233343536373839616263646566&aesIvMask=66656463626139383736353433323130 (0)
[2676:1556:0714/034728:INFO:cast_streaming_apitest.cc(152)] Waiting to encounter 3 more tone(s) and 3 more color(s).
[2676:1556:0714/034728:INFO:cast_streaming_apitest.cc(190)] Heard tone at frequency 200 Hz.
[2676:1556:0714/034728:INFO:cast_streaming_apitest.cc(152)] Waiting to encounter 2 more tone(s) and 3 more color(s).
[2676:1556:0714/034728:INFO:cast_streaming_apitest.cc(237)] Saw color yuv(82, 90, 240).
[2676:1556:0714/034728:INFO:cast_streaming_apitest.cc(152)] Waiting to encounter 2 more tone(s) and 2 more color(s).
[2676:3892:0714/034728:INFO:CONSOLE(70)] "The provided value 'undefined' is not a valid enum value of type OscillatorType.", source: chrome-extension://ddchlicdkolnonkihahngkmmmjnjlkkf/end_to_end_sender.js (70)
[2676:1556:0714/034728:INFO:cast_streaming_apitest.cc(237)] Saw color yuv(145, 54, 34).
[2676:1556:0714/034728:INFO:cast_streaming_apitest.cc(152)] Waiting to encounter 2 more tone(s) and 1 more color(s).
[2676:1556:0714/034728:INFO:cast_streaming_apitest.cc(190)] Heard tone at frequency 500 Hz.
[2676:1556:0714/034728:INFO:cast_streaming_apitest.cc(152)] Waiting to encounter 1 more tone(s) and 1 more color(s).
[2676:3892:0714/034728:INFO:CONSOLE(70)] "The provided value 'undefined' is not a valid enum value of type OscillatorType.", source: chrome-extension://ddchlicdkolnonkihahngkmmmjnjlkkf/end_to_end_sender.js (70)
[2676:1556:0714/034728:INFO:cast_streaming_apitest.cc(237)] Saw color yuv(41, 240, 110).
[2676:1556:0714/034728:INFO:cast_streaming_apitest.cc(152)] Waiting to encounter 1 more tone(s) and 0 more color(s).
[2676:3892:0714/034729:INFO:CONSOLE(70)] "The provided value 'undefined' is not a valid enum value of type OscillatorType.", source: chrome-extension://ddchlicdkolnonkihahngkmmmjnjlkkf/end_to_end_sender.js (70)
[2676:3892:0714/034729:INFO:CONSOLE(70)] "The provided value 'undefined' is not a valid enum value of type OscillatorType.", source: chrome-extension://ddchlicdkolnonkihahngkmmmjnjlkkf/end_to_end_sender.js (70)
[2676:3892:0714/034729:INFO:CONSOLE(70)] "The provided value 'undefined' is not a valid enum value of type OscillatorType.", source: chrome-extension://ddchlicdkolnonkihahngkmmmjnjlkkf/end_to_end_sender.js (70)
[2676:1556:0714/034729:INFO:cast_streaming_apitest.cc(190)] Heard tone at frequency 1800 Hz.
[2676:3892:0714/034729:INFO:user_input_monitor_win.cc(171)] RegisterRawInputDevices() failed for RIDEV_REMOVE: The parameter is incorrect. (0x57)
[2676:2448:0714/034730:WARNING:sqlite_persistent_cookie_store.cc(1358)] Failed to post task from net::SQLitePersistentCookieStore::Backend::FinishedLoadingCookies@e:uild\slave\gpu_win_builderuild\src
et\extras\sqlite\sqlite_persistent_cookie_store.cc:1366 to client_task_runner_.
[2676:2448:0714/034730:WARNING:sqlite_persistent_cookie_store.cc(1358)] Failed to post task from net::SQLitePersistentCookieStore::Backend::LoadKeyAndNotifyInBackground@e:uild\slave\gpu_win_builderuild\src
et\extras\sqlite\sqlite_persistent_cookie_store.cc:545 to client_task_runner_.
[2676:3892:0714/034730:WARNING:url_request_context_getter.cc(43)] URLRequestContextGetter leaking due to no owning thread.
[       OK ] CastStreamingApiTestWithPixelOutput.EndToEnd (6628 ms)
[----------] 1 test from CastStreamingApiTestWithPixelOutput (6628 ms total)

[----------] Global test environment tear-down
[==========] 1 test from 1 test case ran. (6628 ms total)
[  PASSED  ] 1 test.
[2676:3892:0714/034730:FATAL:at_exit.cc(60)] Check failed: !g_top_manager->processing_callbacks_.
Backtrace:
	SetCrashKeyValueImpl [0x03094F27+407401]
	SetCrashKeyValueImpl [0x030513E1+130083]
	SetCrashKeyValueImpl [0x03095E1A+411228]
	SetCrashKeyValueImpl [0x03095D49+411019]
	SetCrashKeyValueImpl [0x0307348B+269517]
	ovly_debug_event [0x015B5790+5025392]
	RelaunchChromeBrowserWithNewCommandLineIfNeeded [0x03A1C59B+7399290]
	RelaunchChromeBrowserWithNewCommandLineIfNeeded [0x03A1C41B+7398906]
	SetCrashKeyValueImpl [0x0306038E+191440]
	SetCrashKeyValueImpl [0x03095C04+410694]
	SetCrashKeyValueImpl [0x03095A43+410245]
	ovly_debug_event [0x017CE325+7223813]
	GetHandleVerifier [0x030E6731+305201]
	IsSandboxedProcess [0x04ACEC8A+12357065]
	SetCrashKeyValueImpl [0x030475D1+89619]
	(No symbol) [0x00E3B49E]
	IsSandboxedProcess [0x04B3E062+12812705]
	BaseThreadInitThunk [0x76CB338A+18]
	RtlInitializeExceptionChain [0x77869902+99]
	RtlInitializeExceptionChain [0x778698D5+54]

Just looked further, and all the builds and runs of tab_capture_end2end_tests have been solidly green. This must just be a fluke.

I mainly wanted you to be aware of that there were some issues that you might want to know about.
Could not motivate assigning to infrastructure trooper in this case.