Fixes shutdown race in mash

ash/mus/accelerator_registrar_impl.cc

Index: ash/mus/accelerator_registrar_impl.cc
diff --git a/ash/mus/accelerator_registrar_impl.cc b/ash/mus/accelerator_registrar_impl.cc
index 0f4502edd45a10198f82d6078d71b4355a497f61..361f8a7f22f6f8ef6060e66a9ee0a62884cb4854 100644
--- a/ash/mus/accelerator_registrar_impl.cc
+++ b/ash/mus/accelerator_registrar_impl.cc
@@ -35,6 +35,7 @@ AcceleratorRegistrarImpl::AcceleratorRegistrarImpl(
       binding_(this, std::move(request)),
       accelerator_namespace_(accelerator_namespace & 0xffff),
       destroy_callback_(destroy_callback) {
+  window_manager_->AddObserver(this);
   binding_.set_connection_error_handler(base::Bind(
       &AcceleratorRegistrarImpl::OnBindingGone, base::Unretained(this)));
 }
@@ -57,6 +58,7 @@ void AcceleratorRegistrarImpl::ProcessAccelerator(uint32_t accelerator_id,
 }
 
 AcceleratorRegistrarImpl::~AcceleratorRegistrarImpl() {
+  window_manager_->RemoveObserver(this);
   RemoveAllAccelerators();
   destroy_callback_.Run(this);
 }
@@ -132,5 +134,15 @@ void AcceleratorRegistrarImpl::RemoveAccelerator(uint32_t accelerator_id) {
     delete this;
 }
 
+void AcceleratorRegistrarImpl::OnAccelerator(uint32_t id,
+                                             const ui::Event& event) {
+  if (OwnsAccelerator(id))
+    ProcessAccelerator(id, event);
+}
+
+void AcceleratorRegistrarImpl::OnWindowTreeClientDestroyed() {
+  delete this;
+}
+
 }  // namespace mus
 }  // namespace ash