[sheriff] Disable...

[sheriff] Disable LoginShelfViewTest.ClickShutdownButtonOnLockScreenWithVerticalInSessionShelf test as flaky

Flakiness dashboard:
https://test-results.appspot.com/dashboards/flakiness_dashboard.html#testType=ash_unittests&tests=ClickShutdownButtonOnLockScreenWithVerticalInSessionShelf
Sample run:
https://ci.chromium.org/p/chrome/builders/ci/linux-chromeos-chrome/3322

TBR=manucornet@chromium.org

Bug: 1053980
Change-Id: If67ea27a99c1940d122d2cceebf1389afc7e82de
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2062281Reviewed-by: Sergey Poromov <poromov@chromium.org>
Commit-Queue: Sergey Poromov <poromov@chromium.org>
Cr-Commit-Position: refs/heads/master@{#742633}

ash/shelf/login_shelf_view_unittest.cc

@@ -422,8 +422,9 @@ TEST_F(LoginShelfViewTest, ClickShutdownButtonOnLockScreen) {
 
 // Tests that shutdown button can be clicked on the lock screen for active
 // session that starts with side shelf. See https://crbug.com/1050192.
+// The test is flaky: https://crbug.com/1053980
 TEST_F(LoginShelfViewTest,
-       ClickShutdownButtonOnLockScreenWithVerticalInSessionShelf) {
+       DISABLED_ClickShutdownButtonOnLockScreenWithVerticalInSessionShelf) {
   CreateUserSessions(1);
   SetShelfAlignmentPref(
       Shell::Get()->session_controller()->GetPrimaryUserPrefService(),