Chrome Version       : 71.0.3572.0
OS Version: 11143.0.0

What steps will reproduce the problem?
1. Use a Pixelbook in notebook configuration
2. Fold screen back and switch to tablet configuration

What is the expected result?

Expect switch to work.


What happens instead of that?

Chrome crashes.
crash/1dcb8047af8528e7

	0x00005b0aa821b9a0	(chrome -./../../../../../../../home/chrome-bot/chrome_root/src/base/observer_list_internal.h:30 )	<name omitted>
0x00005b0aa9283647	(chrome -./../../../../../../../home/chrome-bot/chrome_root/src/ash/wm/window_state.cc:513 )	ash::wm::GetWindowState(aura::Window*)
0x00005b0aa9272cc0	(chrome -./../../../../../../../home/chrome-bot/chrome_root/src/ash/wm/tablet_mode/tablet_mode_window_manager.cc:351 )	ash::TabletModeWindowManager::AddWindow(aura::Window*)
0x00005b0aa96cd0e9	(chrome -./../../../../../../../home/chrome-bot/chrome_root/src/ash/wm/tablet_mode/tablet_mode_controller.cc:215 )	MultiUserWindowManagerChromeOS::OnTabletModeToggled(bool)
0x00005b0aa96e24e4	(chrome -./../../../../../../../home/chrome-bot/chrome_root/src/chrome/browser/ui/ash/tablet_mode_client.cc:80 )	TabletModeClient::OnTabletModeToggled(bool)
0x00005b0aa56623f8	(chrome -./gen/ash/public/interfaces/tablet_mode.mojom.cc:105 )	ash::mojom::TabletModeClientStubDispatch::Accept(ash::mojom::TabletModeClient*, mojo::Message*)
0x00005b0aa6c04e28	(chrome -./../../../../../../../home/chrome-bot/chrome_root/src/mojo/public/cpp/bindings/lib/interface_endpoint_client.cc:423 )	mojo::InterfaceEndpointClient::HandleIncomingMessageThunk::Accept(mojo::Message*)
0x00005b0aa6c0a613	(chrome -./../../../../../../../home/chrome-bot/chrome_root/src/mojo/public/cpp/bindings/lib/interface_endpoint_client.cc:306 )	mojo::internal::MultiplexRouter::ProcessIncomingMessage(mojo::internal::MultiplexRouter::MessageWrapper*, mojo::internal::MultiplexRouter::ClientCallBehavior, base::SequencedTaskRunner*)
0x00005b0aa3dde33d	(chrome -./../../../../../../../home/chrome-bot/chrome_root/src/mojo/public/cpp/bindings/lib/multiplex_router.cc:590 )	mojo::internal::MultiplexRouter::Accept(mojo::Message*)
0x00005b0aa3ddded7	(chrome -./../../../../../../../home/chrome-bot/chrome_root/src/mojo/public/cpp/bindings/lib/connector.cc:476 )	mojo::Connector::ReadAllAvailableMessages()
0x00005b0aa3ddf383	(chrome -./../../../../../../../home/chrome-bot/chrome_root/src/base/callback.h:129 )	mojo::SimpleWatcher::OnHandleReady(int, unsigned int, mojo::HandleSignalsState const&)