ash: Replace SessionStateDelegate::CanAddUserToMultiProfile

ash/common/session/session_types.h

 // Copyright 2015 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_COMMON_SESSION_SESSION_TYPES_H_
 #define ASH_COMMON_SESSION_SESSION_TYPES_H_
 
 namespace ash {
 
 // The index of the user profile to use. The list is always LRU sorted so that
 // index 0 is the currently active user.
 using UserIndex = int;
 
+// Represents possible user adding scenarios.
+enum class AddUserSessionPolicy {
+  // Adding a user is allowed.
+  ALLOWED,
+  // Disallowed due to primary user's policy.
+  ERROR_NOT_ALLOWED_PRIMARY_USER,
+  // Disallowed due to no eligible users.
+  ERROR_OUT_OF_USERS,

[James Cook, 2016/11/18 00:24:08]

optional nit: What about ERROR_NO_ELIGIBLE_USERS? According to the UserManager
docs this not because of a limit on the number of users, but rather than no
current accounts are allowed to do it.

[xiyuan, 2016/11/18 22:05:25]

Sounds good. Done.

+  // Disallowed due to reaching maximum supported user.
+  ERROR_MAXIMUM_USERS_REACHED,
+};
+
 }  // namespace ash
 
 #endif  // ASH_COMMON_SESSION_SESSION_TYPES_H_