The key event should be stopped propagation when it's been processed as an accelerator.

ui/views/widget/native_widget_aura.cc

Index: ui/views/widget/native_widget_aura.cc
diff --git a/ui/views/widget/native_widget_aura.cc b/ui/views/widget/native_widget_aura.cc
index 12b6255aef37b20057298db70b940b3f7b58f890..85ab0aee9c0de3c74cd08d52dc8b9764d3a1a745 100644
--- a/ui/views/widget/native_widget_aura.cc
+++ b/ui/views/widget/native_widget_aura.cc
@@ -873,10 +873,7 @@ void NativeWidgetAura::OnKeyEvent(ui::KeyEvent* event) {
   if (!window_->IsVisible())
     return;
 
-  FocusManager* focus_manager = GetWidget()->GetFocusManager();
   delegate_->OnKeyEvent(event);
-  if (!event->handled() && focus_manager)
-    focus_manager->OnKeyEvent(*event);
   event->SetHandled();
 }