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

ash/system/chromeos/multi_user/try_switching_user.h

Index: ash/system/chromeos/multi_user/try_switching_user.h
diff --git a/ash/system/chromeos/multi_user/try_switching_user.h b/ash/system/chromeos/multi_user/try_switching_user.h
new file mode 100644
index 0000000000000000000000000000000000000000..d4377350f3cafb754deb7a3561dca8ec5e09074e
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+++ b/ash/system/chromeos/multi_user/try_switching_user.h
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+// Copyright 2014 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.
+
+#ifndef ASH_SYSTEM_CHROMEOS_MULTI_USER_MULTI_TRY_SWITCHING_USER_H_
+#define ASH_SYSTEM_CHROMEOS_MULTI_USER_MULTI_TRY_SWITCHING_USER_H_
+
+#include "ash/ash_export.h"
+#include "base/callback.h"
+
+namespace ash {
+
+// Tries to switch to a new user by first checking if desktop casting / sharing
+// is going on, and let the user decide if he wants to terminate it or not.
+// After terminating any desktop sharing operations, the |switch_user| function
+// will be called.
+void ASH_EXPORT TrySwitchingActiveUser(
+    const base::Callback<void()> switch_user);
+
+// Terminates the "DesktopCastingWarning" dialog from a unit tests and |accept|s
+// it. False will be returned if there was no dialog shown.
+bool ASH_EXPORT TestAndTerminateDesktopCastingWarningForTest(bool accept);
+
+}  // namespace chromeos
+
+#endif  // ASH_SYSTEM_CHROMEOS_MULTI_USER_MULTI_TRY_SWITCHING_USER_H_