Chrome Version: 70.0.3507.1
OS: Windows 10

What steps will reproduce the problem?
I had just re-enable sync in a Chrome profile that had been unused for ~4 weeks.  I'm not sure whether any extensions were added/removed over that period.
Crash occurred shortly after re-enabling profile sign-in.

See crash report 563e38e7f0b3a3ba - browser crashed with:
0x551c7e28	(chrome.dll -logging.cc:856 )	logging::LogMessage::~LogMessage()
0x5623de16	(chrome.dll -update_service.cc:141 )	extensions::UpdateService::OnEvent(update_client::UpdateClient::Observer::Events,std::basic_string<char,std::char_traits<char>,std::allocator<char> > const &)
0x566ab7bc	(chrome.dll -update_client.cc:174 )	update_client::UpdateClientImpl::NotifyObservers(update_client::UpdateClient::Observer::Events,std::basic_string<char,std::char_traits<char>,std::allocator<char> > const &)
0x55e25426	(chrome.dll -bind_internal.h:671 )	base::internal::Invoker<base::internal::BindState<void (DevToolsUIBindings::*)(const std::basic_string<char,std::char_traits<char>,std::allocator<char> > &, const base::ListValue &) __attribute__((thiscall)),base::internal::UnretainedWrapper<DevToolsUIBindings> >,void (const std::basic_string<char,std::char_traits<char>,std::allocator<char> > &, const base::ListValue &)>::Run
0x570361b1	(chrome.dll -component.cc:298 )	update_client::Component::NotifyObservers(update_client::UpdateClient::Observer::Events)
0x57036c61	(chrome.dll -component.cc:430 )	update_client::Component::StateUpdateError::DoHandle()
0x570358ed	(chrome.dll -component.cc:324 )	update_client::Component::State::Handle(base::OnceCallback<void >)
0x5703585a	(chrome.dll -component.cc:188 )	update_client::Component::Handle(base::OnceCallback<void >)
0x56b8a0a1	(chrome.dll -update_engine.cc:331 )	update_client::UpdateEngine::HandleComponent(scoped_refptr<update_client::UpdateContext>)
0x557e0900	(chrome.dll -bind_internal.h:516 )	base::internal::FunctorTraits<void (ChromeProcessSingleton::*)(base::RepeatingCallback<void ()>) __attribute__((thiscall)),void>::Invoke<void (ChromeProcessSingleton::*)(base::RepeatingCallback<void ()>) __attribute__((thiscall)),ChromeProcessSingleton *,base::RepeatingCallback<void ()> >
0x55e6f1d9	(chrome.dll -bind_internal.h:658 )	base::internal::Invoker<base::internal::BindState<void (content::IndexedDBDatabaseCallbacks::IOThreadHelper::*)(mojo::StructPtr<indexed_db::mojom::ObserverChanges>) __attribute__((thiscall)),base::internal::UnretainedWrapper<content::IndexedDBDatabaseCallbacks::IOThreadHelper>,mojo::StructPtr<indexed_db::mojom::ObserverChanges> >,void ()>::RunOnce
0x550cce65	(chrome.dll -task_annotator.cc:101 )	base::debug::TaskAnnotator::RunTask(char const *,base::PendingTask *)
0x550cf856	(chrome.dll -message_loop.cc:427 )	base::MessageLoop::RunTask(base::PendingTask *)
0x550cf652	(chrome.dll -message_loop.cc:438 )	base::MessageLoop::DeferOrRunPendingTask(base::PendingTask)
0x5504d83e	(chrome.dll -message_loop.cc:510 )	base::MessageLoop::DoWork()
0x551482a7	(chrome.dll -message_pump_win.cc:171 )	base::MessagePumpForUI::DoRunLoop()
0x5504d6b0	(chrome.dll -message_pump_win.cc:52 )	base::MessagePumpWin::Run(base::MessagePump::Delegate *)
0x5504d607	(chrome.dll -message_loop.cc:379 )	base::MessageLoop::Run(bool)
0x5504d2c3	(chrome.dll -run_loop.cc:102 )	base::RunLoop::Run()
0x553f7e67	(chrome.dll -chrome_browser_main.cc:2092 )	ChromeBrowserMainParts::MainMessageLoopRun(int *)
0x553f7cbc	(chrome.dll -browser_main_loop.cc:1034 )	content::BrowserMainLoop::RunMainMessageLoopParts()
0x553f7c63	(chrome.dll -browser_main_runner_impl.cc:162 )	content::BrowserMainRunnerImpl::Run()
0x55dd974c	(chrome.dll -browser_main.cc:47 )	content::BrowserMain(content::MainFunctionParams const &)
0x563b424f	(chrome.dll -content_main_runner_impl.cc:596 )	content::RunBrowserProcessMain(content::MainFunctionParams const &,content::ContentMainDelegate *)
0x563b4585	(chrome.dll -content_main_runner_impl.cc:947 )	content::ContentMainRunnerImpl::Run(bool)
0x5504967c	(chrome.dll -content_service_manager_main_delegate.cc:53 )	content::ContentServiceManagerMainDelegate::RunEmbedderProcess()
0x55035f91	(chrome.dll -main.cc:472 )	service_manager::Main(service_manager::MainParams const &)
0x55035953	(chrome.dll -content_main.cc:19 )	content::ContentMain(content::ContentMainParams const &)
0x55031ee9	(chrome.dll -chrome_main.cc:101 )	ChromeMain
0x00a25e3f	(chrome.exe -main_dll_loader_win.cc:201 )	MainDllLoader::Launch(HINSTANCE__ *,base::TimeTicks)
0x00a2154a	(chrome.exe -chrome_exe_main_win.cc:230 )	wWinMain
0x00aebe09	(chrome.exe -exe_common.inl:283 )	__scrt_common_main_seh
0x768d8673	(KERNEL32.DLL + 0x00018673 )	BaseThreadInitThunk
0x77075d86	(ntdll.dll + 0x00065d86 )	__RtlUserThreadStart
0x77075d56	(ntdll.dll + 0x00065d56 )	_RtlUserThreadStart

This was the NOTREACHED() at https://cs.chromium.org/chromium/src/extensions/browser/updater/update_service.cc?l=141