10644.0.0 (Official Build) dev-channel kevin test
+ ToT Chrome ( 45f1cc8fc585603dac79b02506921c193583e646 )via simple chrome workflow, debug build.

Device has two users.
Wait until login screen is shown, press "Show webui login..." (I used touchpad). Observe crash:

[29261:29261:0503/190036.889249:FATAL:login_shelf_view.cc(221)] Check failed: sender->id() != kShowWebUiLogin. 
#0 0x00000d91a8a8 base::debug::StackTrace::StackTrace()
#1 0x00000d7d3c78 base::debug::StackTrace::StackTrace()
#2 0x00000d800362 logging::LogMessage::~LogMessage()
#3 0x00001227d24c ash::LoginShelfView::ButtonPressed()
#4 0x0000106d51ec views::Button::NotifyClick()
#5 0x0000106d4508 views::Button::OnMouseReleased()
#6 0x000010723e0c views::View::ProcessMouseReleased()
#7 0x000010723a62 views::View::OnMouseEvent()
#8 0x0000106c3b7a views::InkDropHostView::OnMouseEvent()
#9 0x00000ea02d04 ui::EventHandler::OnEvent()
#10 0x0000152eebec ui::ScopedTargetHandler::OnEvent()
#11 0x00000ea02134 ui::EventDispatcher::DispatchEvent()
#12 0x00000ea01660 ui::EventDispatcher::ProcessEvent()
#13 0x00000ea01340 ui::EventDispatcherDelegate::DispatchEventToTarget()
#14 0x00000ea0124e ui::EventDispatcherDelegate::DispatchEvent()
#15 0x00001076a300 views::internal::RootView::OnMouseReleased()
#16 0x000010730d6c views::Widget::OnMouseEvent()
#17 0x000010742660 views::NativeWidgetAura::OnMouseEvent()
#18 0x00000ea02d04 ui::EventHandler::OnEvent()
#19 0x00000ea02134 ui::EventDispatcher::DispatchEvent()
#20 0x00000ea01660 ui::EventDispatcher::ProcessEvent()
#21 0x00000ea01340 ui::EventDispatcherDelegate::DispatchEventToTarget()
#22 0x00000ea0124e ui::EventDispatcherDelegate::DispatchEvent()
#23 0x0000152ed450 ui::EventProcessor::OnEventFromSource()
#24 0x0000152ed62c ui::EventProcessor::OnEventFromSource()
#25 0x0000152ee68e ui::EventSource::DeliverEventToSink()
#26 0x0000152ee1e8 ui::EventSource::SendEventToSink()
#27 0x00001206e09e ash::AshWindowTreeHostPlatform::DispatchEvent()
#28 0x0000089c4962 _ZN4base8internal13FunctorTraitsIMN2ui22PlatformWindowDelegateEFvPNS2_5EventEEvE6InvokeIS7_PS3_JS5_EEEvT_OT0_DpOT1_
#29 0x0000089c48dc _ZN4base8internal12InvokeHelperILb0EvE8MakeItSoIMN2ui22PlatformWindowDelegateEFvPNS4_5EventEEJPS5_S7_EEEvOT_DpOT0_
#30 0x0000089c4884 _ZN4base8internal7InvokerINS0_9BindStateIMN2ui22PlatformWindowDelegateEFvPNS3_5EventEEJNS0_17UnretainedWrapperIS4_EEEEEFvS6_EE7RunImplIS8_NSt3__15tupleIJSA_EEEJLj0EEEEvOT_OT0_NSF_16integer_sequenceIjJXspT1_EEEEOS6_
#31 0x0000089c47d8 _ZN4base8internal7InvokerINS0_9BindStateIMN2ui22PlatformWindowDelegateEFvPNS3_5EventEEJNS0_17UnretainedWrapperIS4_EEEEEFvS6_EE7RunOnceEPNS0_13BindStateBaseES6_
#32 0x000007fb4050 _ZNO4base12OnceCallbackIFvNS_4File5ErrorEEE3RunES2_
#33 0x00000ea06276 ui::DispatchEventFromNativeUiEvent()
#34 0x0000089c42da ui::DrmWindowHost::DispatchEvent()
#35 0x00000e9f2292 ui::PlatformEventSource::DispatchEvent()
#36 0x00000f13af24 ui::EventFactoryEvdev::DispatchUiEvent()
#37 0x00000f13bcd8 ui::EventFactoryEvdev::DispatchMouseButtonEvent()
#38 0x00000f13e5be _ZN4base8internal13FunctorTraitsIMN2ui17EventFactoryEvdevEFvRKNS2_12GamepadEventEEvE6InvokeIS8_NS_7WeakPtrIS3_EEJS4_EEEvT_OT0_DpOT1_
#39 0x00000f13ea88 _ZN4base8internal12InvokeHelperILb1EvE8MakeItSoIMN2ui17EventFactoryEvdevEFvRKNS4_12GamepadEventEENS_7WeakPtrIS5_EEJS6_EEEvOT_OT0_DpOT1_
#40 0x00000f13ee20 _ZN4base8internal7InvokerINS0_9BindStateIMN2ui17EventFactoryEvdevEFvRKNS3_22MouseButtonEventParamsEEJNS_7WeakPtrIS4_EES5_EEEFvvEE7RunImplIS9_NSt3__15tupleIJSB_S5_EEEJLj0ELj1EEEEvOT_OT0_NSG_16integer_sequenceIjJXspT1_EEEE
#41 0x00000f13ed6a _ZN4base8internal7InvokerINS0_9BindStateIMN2ui17EventFactoryEvdevEFvRKNS3_22MouseButtonEventParamsEEJNS_7WeakPtrIS4_EES5_EEEFvvEE7RunOnceEPNS0_13BindStateBaseE
#42 0x00000802b0fc _ZNO4base12OnceCallbackIFvvEE3RunEv
#43 0x00000d7d452e base::debug::TaskAnnotator::RunTask()
#44 0x00000d9518ee base::internal::IncomingTaskQueue::RunTask()
#45 0x00000d8120e4 base::MessageLoop::RunTask()
#46 0x00000d8122cc base::MessageLoop::DeferOrRunPendingTask()
#47 0x00000d81249c base::MessageLoop::DoWork()
#48 0x00000d939842 base::MessagePumpLibevent::Run()
#49 0x00000d811c50 base::MessageLoop::Run()
#50 0x00000d86335e base::RunLoop::Run()
#51 0x00000cffc9fe ChromeBrowserMainParts::MainMessageLoopRun()
#52 0x0000098f8386 content::BrowserMainLoop::RunMainMessageLoopParts()
#53 0x0000098fcf72 content::BrowserMainRunnerImpl::Run()
#54 0x0000098f1ae4 content::BrowserMain()
#55 0x00000cfcbcf8 content::RunNamedProcessTypeMain()
#56 0x00000cfce212 content::ContentMainRunnerImpl::Run()
#57 0x00000cfc79c4 content::ContentServiceManagerMainDelegate::RunEmbedderProcess()
#58 0x00000cfe4bfc service_manager::Main()
#59 0x00000cfcaa2c content::ContentMain()
#60 0x000007e9a7de ChromeMain
#61 0x000007e9a746 main