Once https://chromium-review.googlesource.com/c/chromium/src/+/1351809 lands, running the disabled DetachToBrowserTabDragControllerTest.DragDirectlyToSecondWindow for touch events results in the following on the interactive_ui_tests stage of the linux-chromeos-rel bot:

[12677:12677:0102/143515.956165:FATAL:tab_strip.cc(1919)] Check failed: !tabs.empty().
#0 0x564dcff27abf base::debug::StackTrace::StackTrace()
#1 0x564dcfe876fa logging::LogMessage::~LogMessage()
#2 0x564dd2550d23 TabStrip::CalculateBoundsForDraggedTabs()
#3 0x564dd254507b TabDragController::Detach()
#4 0x564dd254438c TabDragController::DragBrowserToNewTabStrip()
#5 0x564dd2543556 TabDragController::ContinueDragging()
#6 0x564dd25419f5 TabDragController::Drag()
#7 0x564dd254e0a4 TabStrip::ContinueDrag()
#8 0x564dd2552142 TabStrip::OnGestureEvent()
#9 0x564dd04334c9 ui::EventDispatcher::ProcessEvent()
#10 0x564dd04332d5 ui::EventDispatcherDelegate::DispatchEventToTarget()
#11 0x564dd0433230 ui::EventDispatcherDelegate::DispatchEvent()
#12 0x564dd0434232 ui::EventProcessor::OnEventFromSource()
#13 0x564dd04349e7 ui::EventSource::DeliverEventToSink()
#14 0x564dd04347a8 ui::EventSource::SendEventToSinkFromRewriter()
#15 0x564dd04334c9 ui::EventDispatcher::ProcessEvent()
#16 0x564dd04332d5 ui::EventDispatcherDelegate::DispatchEventToTarget()
#17 0x564dd0433230 ui::EventDispatcherDelegate::DispatchEvent()
#18 0x564dd1204356 aura::WindowEventDispatcher::ProcessGestures()
#19 0x564dd12064ba aura::WindowEventDispatcher::PostDispatchEvent()
#20 0x564dd0433257 ui::EventDispatcherDelegate::DispatchEvent()
#21 0x564dd0434232 ui::EventProcessor::OnEventFromSource()
#22 0x564dd04349e7 ui::EventSource::DeliverEventToSink()
#23 0x564dd04347a8 ui::EventSource::SendEventToSinkFromRewriter()
#24 0x564dd11f7de6 aura::WindowTreeClient::OnWindowInputEvent()
#25 0x564dccd02dfd ws::mojom::WindowTreeClientStubDispatch::Accept()
#26 0x564dd0199dd6 mojo::InterfaceEndpointClient::HandleValidatedMessage()
#27 0x564dd01aacc6 mojo::FilterChain::Accept()
#28 0x564dd019b165 mojo::InterfaceEndpointClient::HandleIncomingMessage()
#29 0x564dd01a0b08 mojo::internal::MultiplexRouter::ProcessIncomingMessage()
#30 0x564dd019ff5d mojo::internal::MultiplexRouter::Accept()
#31 0x564dd01aacc6 mojo::FilterChain::Accept()
#32 0x564dd0197be6 mojo::Connector::ReadSingleMessage()
#33 0x564dd01985e1 mojo::Connector::ReadAllAvailableMessages()
#34 0x564dd0198489 mojo::Connector::OnHandleReadyInternal()
#35 0x564dccb910d7 mojo::SimpleWatcher::DiscardReadyState()
#36 0x564dd01b64c2 mojo::SimpleWatcher::OnHandleReady()
#37 0x564dccdb3aa1 _ZN4base8internal7InvokerINS0_9BindStateIMN3viz14GpuServiceImplEFvN3gfx21GenericSharedMemoryIdEiRKN3gpu9SyncTokenEEJNS_7WeakPtrIS4_EES6_iS8_EEEFvvEE7RunImplISC_NSt3__15tupleIJSE_S6_iS8_EEEJLm0ELm1ELm2ELm3EEEEvOT_OT0_NSJ_16integer_sequenceImJXspT1_EEEE
#38 0x564dcff4b9c1 base::debug::TaskAnnotator::RunTask()
#39 0x564dcfe9063f base::MessageLoopImpl::RunTask()
#40 0x564dcfe90c23 base::MessageLoopImpl::DoWork()
#41 0x564dcff467f9 base::MessagePumpLibevent::Run()
#42 0x564dcfe901e8 base::MessageLoopImpl::Run()
#43 0x564dcfeb6f59 base::RunLoop::Run()
#44 0x564dcbda21e9 DetachToBrowserTabDragControllerTest::DragInputTo()
#45 0x564dcbdae43e DetachToBrowserTabDragControllerTest_DragDirectlyToSecondWindow_Test::RunTestOnMainThread()
#46 0x564dcf77beda content::BrowserTestBase::ProxyRunTestOnMainThreadLoop()
#47 0x564dcf25ba46 ChromeBrowserMainParts::PreMainMessageLoopRunImpl()
#48 0x564dcf25a818 ChromeBrowserMainParts::PreMainMessageLoopRun()
#49 0x564dcddfc3a0 chromeos::ChromeBrowserMainPartsChromeos::PreMainMessageLoopRun()
#50 0x564dcd09ebb2 content::BrowserMainLoop::PreMainMessageLoopRun()
#51 0x564dcd55e725 content::StartupTaskRunner::RunAllTasksNow()
#52 0x564dcd09d895 content::BrowserMainLoop::CreateStartupTasks()
#53 0x564dcd0a0d84 content::BrowserMainRunnerImpl::Initialize()
#54 0x564dcd09b8b7 content::BrowserMain()
#55 0x564dcf03209c content::ContentMainRunnerImpl::RunServiceManager()
#56 0x564dcf031ca1 content::ContentMainRunnerImpl::Run()
#57 0x564dd147e3c3 service_manager::Main()
#58 0x564dcf0302d4 content::ContentMain()
#59 0x564dcf77b9c2 content::BrowserTestBase::SetUp()
#60 0x564dcf24baa3 InProcessBrowserTest::SetUp()
#61 0x564dcbf6cd00 testing::Test::Run()
#62 0x564dcbf6da9f testing::TestInfo::Run()
#63 0x564dcbf6dff7 testing::TestCase::Run()
#64 0x564dcbf798a7 testing::internal::UnitTestImpl::RunAllTests()
#65 0x564dcbf79427 testing::UnitTest::Run()
#66 0x564dcfe63529 base::TestSuite::Run()
#67 0x564dcbd46f93 InteractiveUITestSuiteRunner::RunTestSuite()
#68 0x564dcf785e7a content::LaunchTests()
#69 0x564dcf2451b0 LaunchChromeTests()
#70 0x564dcbd46f3d main
#71 0x7f91bf12ff45 __libc_start_main
#72 0x564dcbc1602a _start

Somehow, when we go to detach the tab we're dragging, there are no tabs being dragged.