Sample failed runs:
https://ci.chromium.org/p/chromium/builders/luci.chromium.ci/Win10%20Tests%20x64%20%28dbg%29/392
https://ci.chromium.org/p/chromium/builders/luci.chromium.ci/Win10%20Tests%20x64%20%28dbg%29/388

pennymac@: Please take a look or triage further

Sample logs from failed runs:

[ RUN      ] ProcessMitigationsWin32kTest.CheckWin8Redirection
../../sandbox/win/src/process_mitigations_win32k_unittest.cc(680): error: Expected equality of these values:
  SBOX_TEST_SUCCEEDED
    Which is: 632356865
  runner.RunTest(test_policy_command.c_str())
    Which is: -1073741819
Stack trace:
Backtrace:
	StackTraceGetter::CurrentStackTrace [0x00007FF70A1BAD40+80]
	testing::internal::UnitTestImpl::CurrentOsStackTraceExceptTop [0x00007FF70A1E267A+90]
	testing::internal::AssertHelper::operator= [0x00007FF70A1E202A+90]
	sandbox::ProcessMitigationsWin32kTest_CheckWin8Redirection_Test::TestBody [0x00007FF70A15FCFA+986]
../../sandbox/win/src/process_mitigations_win32k_unittest.cc(682): error: Expected equality of these values:
  SBOX_TEST_SUCCEEDED
    Which is: 632356865
  runner.RunTest(L"CheckWin8MonitorsRedirection")
    Which is: -1073741819
Stack trace:
Backtrace:
	StackTraceGetter::CurrentStackTrace [0x00007FF70A1BAD40+80]
	testing::internal::UnitTestImpl::CurrentOsStackTraceExceptTop [0x00007FF70A1E267A+90]
	testing::internal::AssertHelper::operator= [0x00007FF70A1E202A+90]
	sandbox::ProcessMitigationsWin32kTest_CheckWin8Redirection_Test::TestBody [0x00007FF70A15FDF3+1235]
../../sandbox/win/src/process_mitigations_win32k_unittest.cc(683): error: Expected equality of these values:
  SBOX_TEST_SUCCEEDED
    Which is: 632356865
  runner.RunTest(L"CheckWin8MonitorInfo")
    Which is: -1073741819

Disabling the tests and removing from Sheriff queue.

The following revision refers to this bug:
  https://chromium.googlesource.com/chromium/src.git/+/f1a94879a59c230aa7e688b28d401d5ce0a2a52a

commit f1a94879a59c230aa7e688b28d401d5ce0a2a52a
Author: Guido Urdaneta <guidou@chromium.org>
Date: Mon May 07 14:38:57 2018

Disable flaky ProcessMitigationsWin32kTests

TBR=pennymac@chromium.org

Bug: 840335
Change-Id: I023345430e1eb72038197ae079f880c8515b7598
Reviewed-on: https://chromium-review.googlesource.com/1047205
Reviewed-by: Guido Urdaneta <guidou@chromium.org>
Commit-Queue: Guido Urdaneta <guidou@chromium.org>
Cr-Commit-Position: refs/heads/master@{#556434}
[modify] https://crrev.com/f1a94879a59c230aa7e688b28d401d5ce0a2a52a/sandbox/win/src/process_mitigations_win32k_unittest.cc

Hey Will, do you have time to glance at some Win32k lockdown test flakiness?

Note that this is the new DEBUG Windows bot that was very recently added.  Not sure if this flake was ever seen on release bots.  (Context maybe: crbug/818832#c48)

Thanks!

sure I can look into this, but in the meantime, if these are only failing on dbg bots then the test disable should be gated on a debug build, I'll go ahead and land a CL that re-enables these for release builds.

The following revision refers to this bug:
  https://chromium.googlesource.com/chromium/src.git/+/dcab71553fcd04465c66019eeb1f1f468dd71b28

commit dcab71553fcd04465c66019eeb1f1f468dd71b28
Author: Will Harris <wfh@chromium.org>
Date: Tue May 08 19:33:57 2018

Re-enable win32k lockdown tests in release.

BUG=840335

Change-Id: I1c82bc73808a16e633fe27b2d5a6894de7e9b490
Reviewed-on: https://chromium-review.googlesource.com/1047857
Reviewed-by: Penny MacNeil <pennymac@chromium.org>
Commit-Queue: Will Harris <wfh@chromium.org>
Cr-Commit-Position: refs/heads/master@{#556927}
[modify] https://crrev.com/dcab71553fcd04465c66019eeb1f1f468dd71b28/sandbox/win/src/process_mitigations_win32k_unittest.cc

This is proving hard to debug. I can't repro locally. I also can't repro with my own builds running on swarming.

Looking at link from #1

https://ci.chromium.org/p/chromium/builders/luci.chromium.ci/Win10%20Tests%20x64%20%28dbg%29/392

This is isolate hash b513a8a3223d0d33126d11982edac0da0b961c11

Running the same isolate hash with the same set of dimensions results in a pass (tried a few times)

python tools\swarming_client\swarming.py run -d os Windows-10-15063 -d pool Chrome -d integrity high -d cpu x86-64 -s b513a8a3223d0d33126d11982edac0da0b961c11

https://chromium-swarm.appspot.com/task?id=3d63edfb86f73610

Without a repro this will be hard to fix. I think we should re-enable this test and see if we can find a commonality in failures.