chromeos: Show deprecated accelerator notifications in mash

ash/mus/accelerators/accelerator_controller_delegate_mus.cc

Index: ash/mus/accelerators/accelerator_controller_delegate_mus.cc
diff --git a/ash/mus/accelerators/accelerator_controller_delegate_mus.cc b/ash/mus/accelerators/accelerator_controller_delegate_mus.cc
index 1a89e1409a289b848a8c82cee5f8fc1fdfb57d07..41e30db537986bf72d7ac9bf7b1add3fb124b928 100644
--- a/ash/mus/accelerators/accelerator_controller_delegate_mus.cc
+++ b/ash/mus/accelerators/accelerator_controller_delegate_mus.cc
@@ -145,14 +145,5 @@ void AcceleratorControllerDelegateMus::PerformAction(
   }
 }
 
-void AcceleratorControllerDelegateMus::ShowDeprecatedAcceleratorNotification(
-    const char* const notification_id,
-    int message_id,
-    int old_shortcut_id,
-    int new_shortcut_id) {
-  // TODO: http://crbug.com/630316.
-  NOTIMPLEMENTED();
-}
-
 }  // namespace mus
 }  // namespace ash