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

ash/system/user/tray_user.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/system/user/tray_user.h"
 
 #include "ash/ash_switches.h"
 #include "ash/root_window_controller.h"
 #include "ash/session/session_state_delegate.h"
 #include "ash/shelf/shelf_layout_manager.h"
@@ skipping 75 matching lines @@
   UpdateAfterLoginStatusChange(status);
   return layout_view_;
 }
 
 views::View* TrayUser::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 show only the currently active user.
-  if (multiprofile_index_ && session_state_delegate->IsUserSessionBlocked())
+  // If the screen is locked or a system modal dialog box is shown, show only
+  // the currently active user.
+  if (multiprofile_index_ &&
+      (session_state_delegate->IsUserSessionBlocked() ||
+       Shell::GetInstance()->IsSystemModalWindowOpen()))
     return NULL;
 
   CHECK(user_ == NULL);
 
   int logged_in_users = session_state_delegate->NumberOfLoggedInUsers();
 
   // Do not show more UserView's then there are logged in users.
   if (multiprofile_index_ >= logged_in_users)
     return NULL;
 
@@ skipping 179 matching lines @@
 void TrayUser::UpdateLayoutOfItem() {
   RootWindowController* controller = GetRootWindowController(
       system_tray()->GetWidget()->GetNativeWindow()->GetRootWindow());
   if (controller && controller->shelf()) {
     UpdateAfterShelfAlignmentChange(
         controller->GetShelfLayoutManager()->GetAlignment());
   }
 }
 
 }  // namespace ash