Tray elements behave appropriately on the multiple signin screen (more like lock screen)

ash/shell.cc

 // Copyright (c) 2012 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "ash/shell.h"
 
 #include <algorithm>
 #include <string>
 
 #include "ash/accelerators/accelerator_controller.h"
@@ skipping 1124 matching lines @@
 
 ////////////////////////////////////////////////////////////////////////////////
 // Shell, aura::client::ActivationChangeObserver implementation:
 
 void Shell::OnWindowActivated(aura::Window* gained_active,
                               aura::Window* lost_active) {
   if (gained_active)
     target_root_window_ = gained_active->GetRootWindow();
 }
 
+void Shell::SetSessionStateDelegateForTesting(
+    SessionStateDelegate* session_state_delegate) {
+  session_state_delegate_.reset(session_state_delegate);
+}
+
 }  // namespace ash