When building and runing with dcheck_always_on = true (or Debug):

80601:80601:1117/153236:FATAL:thread_restrictions.cc(38)] Check failed: false. Function marked as IO-only was called from a thread that disallows IO!  If this thread really should be allowed to make IO calls, adjust the call to base::ThreadRestrictions::SetIOAllowed() in this thread's startup.
#0 0x7f0cdff0399e base::debug::StackTrace::StackTrace()
#1 0x7f0cdff1aada logging::LogMessage::~LogMessage()
#2 0x7f0cdff6da14 base::ThreadRestrictions::AssertIOAllowed()
#3 0x7f0cdff12889 base::PathExists()
#4 0x7f0ce21c0d29 chromeos::settings::CupsPrintersHandler::CupsPrintersHandler()
#5 0x7f0ce2004582 settings::MdSettingsUI::MdSettingsUI()
#6 0x7f0ce1f2ee86 (anonymous namespace)::NewWebUI<>()
#7 0x7f0cdf2b22e4 content::WebUIControllerFactoryRegistry::CreateWebUIControllerForURL()
#8 0x7f0cdf294104 content::WebContentsImpl::CreateWebUI()
#9 0x7f0cdf2a12fb content::WebContentsImpl::CreateWebUIForRenderFrameHost()
#10 0x7f0cdefd4018 content::RenderFrameHostImpl::UpdatePendingWebUI()
#11 0x7f0cdefdad7d content::RenderFrameHostManager::UpdateStateForNavigate()
#12 0x7f0cdefda68b content::RenderFrameHostManager::Navigate()
#13 0x7f0cdefc062f content::NavigatorImpl::NavigateToEntry()
#14 0x7f0cdefc0f65 content::NavigatorImpl::NavigateToPendingEntry()
#15 0x7f0cdefb3f17 content::NavigationControllerImpl::NavigateToPendingEntryInternal()
#16 0x7f0cdefaf2b1 content::NavigationControllerImpl::NavigateToPendingEntry()
#17 0x7f0cdefb030e content::NavigationControllerImpl::LoadURLWithParams()
#18 0x7f0ce1fa6c29 (anonymous namespace)::LoadURLInContents()
#19 0x7f0ce1fa664c chrome::Navigate()
#20 0x7f0ce1f99bee Browser::OpenURLFromTab()
#21 0x7f0ce2220d02 BookmarkBarView::ButtonPressed()
#22 0x7f0ce1574142 views::CustomButton::OnMouseReleased()
#23 0x7f0ce15bc8b1 views::InkDropHostView::OnMouseEvent()
#24 0x7f0ce3dbf673 ui::ScopedTargetHandler::OnEvent()
#25 0x7f0ce093034d ui::EventDispatcher::ProcessEvent()
#26 0x7f0ce09301ac ui::EventDispatcherDelegate::DispatchEvent()
#27 0x7f0ce15d7acf views::internal::RootView::OnMouseReleased()
#28 0x7f0ce15adb23 views::Widget::OnMouseEvent()
#29 0x7f0ce15b79c7 views::NativeWidgetAura::OnMouseEvent()
#30 0x7f0ce093034d ui::EventDispatcher::ProcessEvent()
#31 0x7f0ce09301ac ui::EventDispatcherDelegate::DispatchEvent()
#32 0x7f0ce3dbf41e ui::EventProcessor::OnEventFromSource()
#33 0x7f0ce0930f98 ui::EventSource::SendEventToProcessor()
#34 0x7f0ce424f49b aura::WindowTreeHostX11::DispatchXI2Event()
#35 0x7f0ce424ee23 aura::WindowTreeHostX11::DispatchEvent()
#36 0x7f0ce0929d76 ui::PlatformEventSource::DispatchEvent()
#37 0x7f0ce097e731 ui::X11EventSource::ExtractCookieDataDispatchEvent()
#38 0x7f0ce097e660 ui::X11EventSource::DispatchXEvents()
#39 0x7f0ce097e109 ui::(anonymous namespace)::XSourceDispatch()
#40 0x7f0cdbecece5 g_main_context_dispatch
#41 0x7f0cdbecf048 <unknown>
#42 0x7f0cdbecf0ec g_main_context_iteration
#43 0x7f0cdff24566 base::MessagePumpGlib::Run()
#44 0x7f0cdff221e9 base::MessageLoop::RunHandler()
#45 0x7f0cdff43a90 base::RunLoop::Run()
#46 0x7f0cdfb290d9 ChromeBrowserMainParts::MainMessageLoopRun()
#47 0x7f0cdeec58c9 content::BrowserMainLoop::RunMainMessageLoopParts()
#48 0x7f0cdeec8990 content::BrowserMainRunnerImpl::Run()
#49 0x7f0cdeec122e content::BrowserMain()
#50 0x7f0cdfaba6c3 content::ContentMainRunnerImpl::Run()
#51 0x7f0cdfab9140 content::ContentMain()
#52 0x7f0cde0f87c3 ChromeMain
#53 0x7f0cd8103f45 __libc_start_main
#54 0x7f0cde0f8661 <unknown>