chrome --mash on device and on desktop, r468701

[12279:12279:0502/111553.693267:1443876332:FATAL:network_handler.cc(170)] Check failed: ui_proxy_config_service_.get(). 
#0 0x7fbd2e56d1ec base::debug::StackTrace::StackTrace()
#1 0x7fbd2e58227e logging::LogMessage::~LogMessage()
#2 0x7fbd2ef6b101 chromeos::NetworkHandler::ui_proxy_config_service()
#3 0x7fbd3034cede ash::NetworkListView::UpdateNetworkListEntries()
#4 0x7fbd3034c940 ash::NetworkListView::UpdateNetworkListInternal()
#5 0x7fbd3034c054 ash::NetworkListView::Update()
#6 0x7fbd3033f465 ash::tray::NetworkStateListDetailedView::Init()
#7 0x7fbd3030cd56 ash::TrayNetwork::CreateDetailedView()
#8 0x7fbd3029324d ash::SystemTrayBubble::CreateItemViews()
#9 0x7fbd30292f19 ash::SystemTrayBubble::UpdateView()
#10 0x7fbd30291585 ash::SystemTray::ShowItems()
#11 0x7fbd30291919 ash::SystemTray::ShowDetailedView()
#12 0x7fbd2e5d2d53 base::Timer::RunScheduledTask()
#13 0x7fbd2e5fdbc6 base::debug::TaskAnnotator::RunTask()
#14 0x7fbd2e587ebe base::MessageLoop::RunTask()
#15 0x7fbd2e58827b base::MessageLoop::DeferOrRunPendingTask()
#16 0x7fbd2e5889d2 base::MessageLoop::DoDelayedWork()
#17 0x7fbd2e589ded base::MessagePumpLibevent::Run()
#18 0x7fbd2e587b2b base::MessageLoop::RunHandler()
#19 0x7fbd2e5a96a0 base::RunLoop::Run()
#20 0x7fbd2e1f33b7 _ZN4base8internal7InvokerINS0_9BindStateIZN15service_manager12_GLOBAL__N_110RunServiceEPNS3_12MainDelegateEE3$_0JS6_PiEEEFvN4mojo16InterfaceRequestINS3_5mojom7ServiceEEEEE3RunEPNS0_13BindStateBaseEOSE_
#21 0x7fbd2ccb1884 service_manager::RunStandaloneService()
#22 0x7fbd2e1f2be9 service_manager::Main()
#23 0x7fbd2e1d39b1 content::ContentMain()
#24 0x7fbd2c91163e ChromeMain
#25 0x7fbd2a3b3796 __libc_start_main
#26 0x7fbd2c911469 _start

It's a CHECK failure on a null ui_proxy_config_service() here:

std::unique_ptr<std::set<std::string>>
NetworkListView::UpdateNetworkListEntries() {
  NetworkStateHandler* handler = NetworkHandler::Get()->network_state_handler();

  // Keep an index where the next child should be inserted.
  int index = 0;

  bool show_connection_warning =
      !!NetworkHandler::Get()->network_state_handler()->ConnectedNetworkByType(
          NetworkTypePattern::VPN());
  show_connection_warning =
      show_connection_warning || NetworkHandler::Get()
                                     ->ui_proxy_config_service()
                                     ->HasDefaultNetworkProxyConfigured();
....

This probably means this code is not covered by tests, otherwise mash_unittests would have caught it.

I don't know if we expect to have a ui_proxy_config_service() with mash or not.