Is there a trybot which we can use to repro this?

Not currently :(

https://bugs.chromium.org/p/chromium/issues/detail?id=514857

Bot is green now...

https://uberchromegw.corp.google.com/i/chromium.android/builders/KitKat%20Tablet%20Tester/

... so maybe this fixed itself. Not really sure.

I checked again and cannot find the problem. I will keep an eye on it for sure.

Most of the Quic-tests in net_unittests look flaky:
https://test-results.appspot.com/dashboards/flakiness_dashboard.html#testType=net_unittests&builder=chromium.android%3AKitKat%20Tablet%20Tester

Example failing test from KitKat Tablet Tester build #6053:
https://uberchromegw.corp.google.com/i/chromium.android/builders/KitKat%20Tablet%20Tester/builds/6053


 
[FATAL:quic_chromium_client_session.cc(857)] Check failed: connect_timing_.connect_start < connect_timing_.connect_end. 

Stack Trace:
  RELADDR   FUNCTION                                                                                                                                                                                        FILE:LINE
  00d81347  logging::LogMessage::~LogMessage()+234                                                                                                                                                          /b/c/b/Android_arm_Builder__dbg_/src/base/logging.cc:532
  00c7aab3  net::QuicChromiumClientSession::OnCryptoHandshakeEvent(net::QuicSession::CryptoHandshakeEvent)+190                                                                                              /b/c/b/Android_arm_Builder__dbg_/src/net/quic/chromium/quic_chromium_client_session.cc:857
  0085d539  net::MockCryptoClientStream::CryptoConnect()+416                                                                                                                                                /b/c/b/Android_arm_Builder__dbg_/src/net/quic/test_tools/mock_crypto_client_stream.cc:93
  00c77ff9  net::QuicChromiumClientSession::CryptoConnect(bool, base::Callback<void (int), (base::internal::CopyMode)1, (base::internal::RepeatMode)1> const&)+48                                           /b/c/b/Android_arm_Builder__dbg_/src/net/quic/chromium/quic_chromium_client_session.cc:662
  00660df3  net::test::(anonymous namespace)::QuicChromiumClientSessionTest::CompleteCryptoHandshake()+22                                                                                                   /b/c/b/Android_arm_Builder__dbg_/src/net/quic/chromium/quic_chromium_client_session_test.cc:144
  006688b5  net::test::(anonymous namespace)::QuicChromiumClientSessionTest_MigrateToSocketMaxReaders_Test::TestBody()+36                                                                                   /b/c/b/Android_arm_Builder__dbg_/src/net/quic/chromium/quic_chromium_client_session_test.cc:702
  0170f191  testing::Test::Run()+108                                                                                                                                                                        /b/c/b/Android_arm_Builder__dbg_/src/testing/gtest/src/gtest.cc:2475
  0170f2cf  testing::TestInfo::Run()+242                                                                                                                                                                    /b/c/b/Android_arm_Builder__dbg_/src/testing/gtest/src/gtest.cc:2656
  0170f35b  testing::TestCase::Run()+114                                                                                                                                                                    /b/c/b/Android_arm_Builder__dbg_/src/testing/gtest/src/gtest.cc:2774
  01711dff  testing::internal::UnitTestImpl::RunAllTests()+442                                                                                                                                              /b/c/b/Android_arm_Builder__dbg_/src/testing/gtest/src/gtest.cc:4647
  v------>  bool testing::internal::HandleExceptionsInMethodIfSupported<testing::internal::UnitTestImpl, bool>(testing::internal::UnitTestImpl*, bool (testing::internal::UnitTestImpl::*)(), char const*)  /b/c/b/Android_arm_Builder__dbg_/src/testing/gtest/src/gtest.cc:2458
  0170b573  testing::UnitTest::Run()+98                                                                                                                                                                     /b/c/b/Android_arm_Builder__dbg_/src/testing/gtest/src/gtest.cc:4258
  v------>  RUN_ALL_TESTS()                                                                                                                                                                                 /b/c/b/Android_arm_Builder__dbg_/src/testing/gtest/include/gtest/gtest.h:2237
  0174436f  base::TestSuite::Run()+86                                                                                                                                                                       /b/c/b/Android_arm_Builder__dbg_/src/base/test/test_suite.cc:246
  v------>  LaunchUnitTestsInternal                                                                                                                                                                         /b/c/b/Android_arm_Builder__dbg_/src/base/test/launcher/unit_test_launcher.cc:187
  01750a43  base::LaunchUnitTests(int, char**, base::Callback<int (), (base::internal::CopyMode)1, (base::internal::RepeatMode)1> const&)+54                                                                /b/c/b/Android_arm_Builder__dbg_/src/base/test/launcher/unit_test_launcher.cc:458
  001ef25f  main+162                                                                                                                                                                                        /b/c/b/Android_arm_Builder__dbg_/src/net/test/run_all_unittests.cc:54
  v------>  RunTests                                                                                                                                                                                        /b/c/b/Android_arm_Builder__dbg_/src/testing/android/native_test/native_test_launcher.cc:136
  016c5497  Java_org_chromium_native_1test_NativeTest_nativeRunTests+654                                                                                                                                    /b/c/b/Android_arm_Builder__dbg_/src/out/Debug/gen/testing/android/native_test/native_test_jni_headers/testing/jni/NativeTest_jni.h:56
  0001dbcf  <unknown>                                                                                                                                                                                       /system/lib/libdvm.so
  0004e125  <unknown>                                                                                                                                                                                       .
.
.



There are 20 tests failing with "Check failed: connect_timing_.connect_start < connect_timing_.connect_end. " in that run.

Hmmm, currently, I have no idea how this can happen with https://codereview.chromium.org/2487613002

Keep investigating.

[FATAL:quic_chromium_client_session.cc(857)] Check failed: connect_timing_.connect_start < connect_timing_.connect_end. 

I wonder if that were changed from < to <= if that would solve the issue? fayang, you could consider changing that from:

    DCHECK(connect_timing_.connect_start < connect_timing_.connect_end);

to

    DCHECK_LE(connect_timing_.connect_start, connect_timing_.connect_end);

So we could see the values if it fails.