ToT chromeos-linux-simulator

out/Default/chrome --ash-host-window-bounds="1200x800,1250+0-1200x800" --user-data-dir=/w/udd --ash-dev-shortcuts --ash-debug-shortcuts --mash

* Open system tray on second monitor
* Click on ethernet item

Received signal 11 SEGV_MAPERR 0000000000a8
#0 0x7fb1fe75e47d base::debug::StackTrace::StackTrace()
#1 0x7fb1fe75c9fc base::debug::StackTrace::StackTrace()
#2 0x7fb1fe75de77 base::debug::(anonymous namespace)::StackDumpSignalHandler()
#3 0x7fb1fed45330 <unknown>
#4 0x7fb1f34e84fc aura::Window::IsRootWindow()
#5 0x7fb1f3570db9 aura::Window::GetRootWindow()
#6 0x7fb1f3570e35 aura::Window::GetHost()
#7 0x7fb1f356efc5 aura::Window::GetHost()
#8 0x7fb1ef05f1a5 ash::WindowManager::OnPointerEventObserved()
#9 0x7fb1f354422f aura::WindowTreeClient::OnPointerEventObserved()
#10 0x7fb1f3638186 ui::mojom::WindowTreeClientStubDispatch::Accept()
#11 0x7fb1f3557c03 ui::mojom::WindowTreeClientStub<>::Accept()
#12 0x7fb1fce6c15b mojo::InterfaceEndpointClient::HandleValidatedMessage()
#13 0x7fb1fce6acc1 mojo::InterfaceEndpointClient::HandleIncomingMessageThunk::Accept()
#14 0x7fb1fce69362 mojo::FilterChain::Accept()
#15 0x7fb1fce6eaef mojo::InterfaceEndpointClient::HandleIncomingMessage()
#16 0x7fb1fce84e0b mojo::internal::MultiplexRouter::ProcessIncomingMessage()

Relevant source:
  // We have received a pointer event on |target|. However, we need to fixup
  // |target| first. WindowManager's WindowTree is the entire root tree and
  // we must adjust |target| from being the root to the aura::Window which
  // would handle |event|.
  std::unique_ptr<ui::Event> event_copy = ui::Event::Clone(event);
  ui::EventTarget* e_target =
      target->GetHost()
          ->dispatcher()
          ->GetDefaultEventTargeter()
          ->FindTargetForEvent(target, event_copy.get());

  pointer_watcher_event_router_->OnPointerEventObserved(
      event, static_cast<aura::Window*>(e_target));

Maybe |target| is null sometimes?

erg, can you take a look? I think you added this code recently. Feel free to bounce back to me if it's not related.