mus: Crash on shutdown in unified desktop mode

On ToT @ #532045 linux desktop chrome os:
(1) Run chrome --ash-enable-unified-desktop --ash-host-window-bounds=400x400,450+0-400x400 --mus
(2) Shut down via the system tray menu option
Expected: Clean shutdown
Actual: Crash!

Received signal 11 SEGV_MAPERR ffffefdc1e79097c
#0 0x7f65203494ec base::debug::StackTrace::StackTrace()
#1 0x7f6520348fe1 base::debug::(anonymous namespace)::StackDumpSignalHandler()
#2 0x7f65204d50c0 <unknown>
#3 0x7f651c8ade40 cc::TextureLayer::SetTransferableResourceInternal()
#4 0x7f651c8ad9c7 cc::TextureLayer::ClearClient()
#5 0x7f651bd4f601 ui::Layer::SwitchToLayer()
#6 0x7f651bd50bb1 ui::Layer::SetShowSolidColorContent()
#7 0x7f651db0b23b content::ReflectorImpl::DetachFromOutputSurface()
#8 0x7f651db0b0ec content::ReflectorImpl::Shutdown()
#9 0x7f651db07655 content::GpuProcessTransportFactory::RemoveReflector()
#10 0x7f651a8381ad ash::MirrorWindowController::Close()
#11 0x7f651a8382a1 ash::MirrorWindowController::~MirrorWindowController()
#12 0x7f651a845ea3 ash::WindowTreeHostManager::Shutdown()
#13 0x7f651a8dd350 ash::Shell::~Shell()
#14 0x7f651a8de4ce ash::Shell::~Shell()
#15 0x7f651a97fbc1 ash::WindowManager::~WindowManager()
#16 0x7f651a97fdfe ash::WindowManager::~WindowManager()
#17 0x55b88ab1acad ChromeBrowserMainExtraPartsAsh::PostMainMessageLoopRun()
#18 0x55b8899297aa ChromeBrowserMainParts::PostMainMessageLoopRun()
#19 0x55b8895235e1 chromeos::ChromeBrowserMainPartsChromeos::PostMainMessageLoopRun()
#20 0x7f651d5c875d content::BrowserMainLoop::ShutdownThreadsAndCleanUp()
#21 0x7f651d5cbaf0 content::BrowserMainRunnerImpl::Shutdown()
#22 0x7f651d5c41b6 content::BrowserMain()