ash: Add SessionController/Client mojo interfaces

ash/public/interfaces/session_controller.mojom

Index: ash/public/interfaces/session_controller.mojom
diff --git a/ash/public/interfaces/session_controller.mojom b/ash/public/interfaces/session_controller.mojom
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+// Copyright 2016 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.
+
+module ash.mojom;
+
+import "skia/public/interfaces/bitmap.mojom";
+
+// Matches session_manager::SessionState.
+[Extensible]

[James Cook, 2016/12/06 18:08:25]

Per offline conversation I don't think these should be [extensible], at least
not yet.

[xiyuan, 2016/12/06 19:24:21]

Done.

+enum SessionState {
+  // Default value, when session state hasn't been initialized yet.
+  UNKNOWN,
+
+  // Running out of box UI.
+  OOBE,
+
+  // Running login UI (primary user) but user sign in hasn't completed yet.
+  LOGIN_PRIMARY,
+
+  // Running login UI (primary or secondary user), user sign in has been
+  // completed but login UI hasn't been hidden yet. This means that either
+  // some session initialization is happening or user has to go through some
+  // UI flow on the same login UI like select avatar, agree to terms of
+  // service etc.
+  LOGGED_IN_NOT_ACTIVE,
+
+  // A user(s) has logged in *and* login UI is hidden i.e. user session is
+  // not blocked.
+  ACTIVE,
+
+  // The session screen is locked.
+  LOCKED,
+
+  // Same as SESSION_STATE_LOGIN_PRIMARY but for multi-profiles sign in i.e.
+  // when there's at least one user already active in the session.
+  LOGIN_SECONDARY,
+};
+
+// Matches user_manager::UserType.
+[Extensible]
+enum UserType {
+  // Regular user, has a user name and password.
+  REGULAR,
+
+  // Guest user, logs in without authentication.
+  GUEST,
+
+  // Public account user, logs in without authentication. Available only if
+  // enabled through policy.
+  PUBLIC_ACCOUNT,
+
+  // Supervised user, logs in only with local authentication.
+  SUPERVISED,
+
+  // Kiosk app robot, logs in without authentication.
+  KIOSK,
+
+  // Child user, with supervised options.
+  CHILD,
+
+  // Android app in kiosk mode, logs in without authentication.
+  ARC_KIOSK,
+};
+
+// Info about a user session in ash.
+struct UserSession {
+  uint32 session_id;

[James Cook, 2016/12/06 18:08:25]

Is this a general id used throughout chrome, or just for the ash/chrome
communication? Can you document what it means?

[xiyuan, 2016/12/06 19:24:21]

The concept of the user session id does not exist yet. Currently, the
UserManager tracks the user sessions in two list: GetLoggedInUsers and
GetLRULoggedInUsers. GetLoggedInUsers returns a list that corresponding the
order of user logins. The order of the list never changes. I will be moving
tracking code from UserManager to SessionManager. The SessionManager will
generate a session id when a user session is created during login. The session
id would be same as the 1 + index of the list returned from GetLoggedInUsers.
The session id would be used throughout chrome to reference user sessions after
the change.

Added documentation.

+  UserType type;
+  string account_id;  // Serialized AccountId
+  string display_name;
+  string display_email;
+  skia.mojom.Bitmap avatar;
+};
+
+// Matches ash::AddUserSessionPolicy.
+[Extensible]
+enum AddUserSessionPolicy {
+  // Adding a user session is allowed.
+  ALLOWED,
+
+  // Disallowed due to primary user's policy.
+  ERROR_NOT_ALLOWED_PRIMARY_USER,
+
+  // Disallowed due to no eligible users.
+  ERROR_NO_ELIGIBLE_USERS,
+
+  // Disallowed due to reaching maximum supported user.
+  ERROR_MAXIMUM_USERS_REACHED,
+};
+
+// Info about an ash session.
+struct SessionInfo {
+  // Maximum possible number of logged in users in ash.
+  uint32 max_users;
+
+  // Whether the screen can be locked.
+  bool can_lock_screen;
+
+  // Whether the screen should be locked automatically before suspending.
+  bool should_lock_screen_automatically;
+
+  // Sets whether adding a user session to ash is allowed.
+  AddUserSessionPolicy add_user_session_policy;
+
+  // Current state of the ash session.
+  SessionState state;
+};
+
+// Interface for ash client (e.g. Chrome) to set session info for ash.
+interface SessionController {
+  // Sets the client interface.
+  SetClient(SessionControllerClient client);
+
+  // Sets the ash session info.
+  SetSessionInfo(SessionInfo info);
+
+  // Updates a user session. This is called when a user session is added or
+  // its meta data (e.g. name, avatar) is changed.

[James Cook, 2016/12/06 18:08:25]

nit: Comment that there is no method to remove a user because ash/chrome doesn't
support that -- all users are logged out at once.

[xiyuan, 2016/12/06 19:24:21]

Done.

+  UpdateUserSession(UserSession user_session);
+
+  // Sets the order of user sessions. The order is keyed by the session id
+  // and is LRU sorted with the first being the currently active user session.
+  SetUserSessionOrder(array<uint32> user_session_order);

[James Cook, 2016/12/06 18:08:25]

I like this approach.

nit: maybe make the parameter user_session_ids (or similar) to emphasize that
the ints are ids

[xiyuan, 2016/12/06 19:24:21]

Done.

+};
+
+// Interface for ash to request session service from its client (e.g. Chrome).
+interface SessionControllerClient {
+  // Requests to lock screen.
+  RequestLockScreen();
+
+  // Switch to the active user with |account_id| (if the user has already signed
+  // in).
+  SwitchActiveUser(string account_id);
+
+  // Switch the active user to the next or previous user.
+  CycleActiveUser(bool next_user);
+};