cros: Make sure views-based lock screen is destroyed after it is dismissed.

ash/login/mock_lock_screen_client.cc

Index: ash/login/mock_lock_screen_client.cc
diff --git a/ash/login/mock_lock_screen_client.cc b/ash/login/mock_lock_screen_client.cc
index 364f90cd6c64223f64ebaf4d77b21cb33a6c1715..934c18577e2243404dd9d89c41989bf859ba5097 100644
--- a/ash/login/mock_lock_screen_client.cc
+++ b/ash/login/mock_lock_screen_client.cc
@@ -17,6 +17,14 @@ mojom::LockScreenClientPtr MockLockScreenClient::CreateInterfacePtrAndBind() {
   return binding_.CreateInterfacePtrAndBind();
 }
 
+void MockLockScreenClient::AuthenticateUser(const AccountId& account_id,
+                                            const std::string& password,
+                                            bool authenticated_by_pin,
+                                            AuthenticateUserCallback callback) {
+  AuthenticateUser_(account_id, password, authenticated_by_pin, callback);
+  std::move(callback).Run(authenticate_user_callback_result_);
+}
+
 std::unique_ptr<MockLockScreenClient> BindMockLockScreenClient() {
   LockScreenController* lock_screen_controller =
       Shell::Get()->lock_screen_controller();