It seems to be flaky: https://test-results.appspot.com/dashboards/flakiness_dashboard.html#tests=LayerTreeHostTestBeginFrameSequenceNumbers.RunMultiThread_DelegatingRenderer&testType=cc_unittests

This is a failed pass: https://build.chromium.org/p/chromium.win/builders/Win7%20Tests%20%28dbg%29%281%29/builds/57954

This is the log when the failure happens:

LayerTreeHostTestBeginFrameSequenceNumbers.RunMultiThread_DelegatingRenderer (run #1):
[ RUN      ] LayerTreeHostTestBeginFrameSequenceNumbers.RunMultiThread_DelegatingRenderer
Backtrace:
	cc::LayerTreeHostImplForTesting::`vcall'{0}' [0x011BF7AB+2]
	base::internal::InvokeHelper<0,void>::MakeItSo<void (__thiscall cc::LayerTreeHostImplForTesting::*const &)(void),cc::LayerTreeHostImplForTesting *> [0x011BD0E8+40]
	base::internal::Invoker<base::internal::BindState<void (__thiscall cc::LayerTreeHostImplForTesting::*)(void),base::internal::UnretainedWrapper<cc::LayerTreeHostImplForTesting> >,void __cdecl(void)>::RunImpl<void (__thiscall cc::LayerTreeHostImplForTesting [0x011BD4DB+59]
	base::internal::Invoker<base::internal::BindState<void (__thiscall cc::LayerTreeHostImplForTesting::*)(void),base::internal::UnretainedWrapper<cc::LayerTreeHostImplForTesting> >,void __cdecl(void)>::Run [0x011C34D4+36]
	base::internal::RunMixin<base::Callback<void __cdecl(void),0,0> >::Run [0x0282C5A4+68]
	base::debug::TaskAnnotator::RunTask [0x0282C7AF+479]
	base::MessageLoop::RunTask [0x028A36B2+626]
	base::MessageLoop::DeferOrRunPendingTask [0x028A174C+44]
	base::MessageLoop::DoWork [0x028A1D22+242]
	base::MessagePumpDefault::Run [0x028A96F0+144]
	base::MessageLoop::RunHandler [0x028A33CE+398]
	base::RunLoop::Run [0x02956D46+166]
	base::Thread::Run [0x029EFB81+273]
	base::Thread::ThreadMain [0x029F0C1F+863]
	base::PlatformThread::Sleep [0x029CBCDC+380]
	BaseThreadInitThunk [0x76BC337A+18]
	RtlInitializeExceptionChain [0x779592B2+99]
	RtlInitializeExceptionChain [0x77959285+54]

LayerTreeHostTestBeginFrameSequenceNumbers.RunMultiThread_DelegatingRenderer (run #2):
[ RUN      ] LayerTreeHostTestBeginFrameSequenceNumbers.RunMultiThread_DelegatingRenderer
c:\c\win\src\cc	rees\layer_tree_host_unittest.cc(7091): error: Value of: frame_data_->begin_frame_ack
  Actual: BeginFrameAck(1, 5, 5, 0, 1)
Expected: BeginFrameAck(current_begin_frame_args_.source_id, current_begin_frame_args_.sequence_number, current_begin_main_frame_args_on_impl_.sequence_number, 0, true)
Which is: BeginFrameAck(1, 5, 2, 0, 1)
[  FAILED  ] LayerTreeHostTestBeginFrameSequenceNumbers.RunMultiThread_DelegatingRenderer (54 ms)

danakj: Could you please help triage? Thanks!

Based on https://findit-for-me.appspot.com/waterfall/check-flake?key=ag9zfmZpbmRpdC1mb3ItbWVy0wELEhdNYXN0ZXJGbGFrZUFuYWx5c2lzUm9vdCKcAWNocm9taXVtLndpbi9XaW43IFRlc3RzIChkYmcpKDEpLzU3OTU0L2NjX3VuaXR0ZXN0cy9UR0Y1WlhKVWNtVmxTRzl6ZEZSbGMzUkNaV2RwYmtaeVlXMWxVMlZ4ZFdWdVkyVk9kVzFpWlhKekxsSjFiazExYkhScFZHaHlaV0ZrWDBSbGJHVm5ZWFJwYm1kU1pXNWtaWEpsY2c9PQwLEhNNYXN0ZXJGbGFrZUFuYWx5c2lzGAEM , the culprit is r455194 in which the test was added.

Fix is pending in https://codereview.chromium.org/2738183002/

The following revision refers to this bug:
  https://chromium.googlesource.com/chromium/src.git/+/d4b3ea55a73c7053a9591e1c0c6fba6e85e166da

commit d4b3ea55a73c7053a9591e1c0c6fba6e85e166da
Author: eseckler <eseckler@chromium.org>
Date: Mon Mar 13 23:11:06 2017

[cc] Fix LayerTreeHostTestBeginFrameSequenceNumbers flakiness.

DrawLayersOnThread and DisplayReceivedCompositorFrameOnThread were being
called for the second commit during shutdown of the test after EndTest(),
causing the expectations within to fail. Added early outs.

Also, DrawLayersOnThread is called after the draw has completed and,
thus, after the compositor frame was submitted. Fixed the expected
ordering in the test.

BUG= 699640 
CQ_INCLUDE_TRYBOTS=master.tryserver.blink:linux_trusty_blink_rel

Review-Url: https://codereview.chromium.org/2738183002
Cr-Commit-Position: refs/heads/master@{#456528}

[modify] https://crrev.com/d4b3ea55a73c7053a9591e1c0c6fba6e85e166da/cc/trees/layer_tree_host_unittest.cc

Flakiness should go down now. Please reopen if that's not the case.