Multiprofile security: Show a warning messagebox when desktop casting/sharing is turned on upon user

ash/system/user/tray_user_separator.cc

 // Copyright 2013 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/system/user/tray_user_separator.h"
 
 #include "ash/session/session_state_delegate.h"
 #include "ash/shell.h"
 #include "ui/views/view.h"
 
 namespace ash {
 
 TrayUserSeparator::TrayUserSeparator(SystemTray* system_tray)
     : SystemTrayItem(system_tray),
       separator_shown_(false) {
 }
 
 views::View* TrayUserSeparator::CreateTrayView(user::LoginStatus status) {
   return NULL;
 }
 
 views::View* TrayUserSeparator::CreateDefaultView(user::LoginStatus status) {
   if (status == user::LOGGED_IN_NONE)
     return NULL;
 
   const SessionStateDelegate* session_state_delegate =
       Shell::GetInstance()->session_state_delegate();
 
-  // If the screen is locked, or only a single user is shown, show nothing.
+  // If the screen is locked, a system modal dialog or a single user is shown,
+  // show nothing.
   if (session_state_delegate->IsUserSessionBlocked() ||
+      Shell::GetInstance()->IsSystemModalWindowOpen() ||
       session_state_delegate->NumberOfLoggedInUsers() < 2)
     return NULL;
 
   separator_shown_ = true;
   return new views::View();
 }
 
 views::View* TrayUserSeparator::CreateDetailedView(user::LoginStatus status) {
   return NULL;
 }
 
 void TrayUserSeparator::DestroyDefaultView() {
   separator_shown_ = false;
 }
 
 }  // namespace ash