ash: Add SessionController/Client mojo interfaces

ash/public/interfaces/session_controller.mojom

+// 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

[James Cook, 2016/12/01 23:01:43]

super nit: end with . (and below) for consistency

[xiyuan, 2016/12/06 00:46:34]

Done.

+[Extensible]
+enum SessionState {
+  UNKNOWN,

[James Cook, 2016/12/01 23:01:43]

nit: Please copy the comments for these enum values (this and below) into the
mojom file. Mojoms should be long-lived interfaces and have the best possible
documentation.

[xiyuan, 2016/12/06 00:46:34]

Done.

+  OOBE,
+  LOGIN_PRIMARY,
+  LOGGED_IN_NOT_ACTIVE,
+  ACTIVE,
+  LOCKED,
+  LOGIN_SECONDARY,
+};
+
+// Matches user_manager::UserType.
+[Extensible]
+enum UserType {
+  REGULAR,
+  GUEST,
+  PUBLIC_ACCOUNT,
+  SUPERVISED,
+  KIOSK,
+  CHILD,
+  ARC_KIOSK,
+};
+
+// Info about a user session in ash.
+struct UserSession {
+  UserType type;
+  string account_id;  // Serialized AccountId
+  string display_name;
+  string display_email;
+  skia.mojom.Bitmap avatar;
+};
+
+// Matches ash::AddUserSessionPolicy
+[Extensible]
+enum AddUserSessionPolicy {
+  ALLOWED,
+  ERROR_NOT_ALLOWED_PRIMARY_USER,
+  ERROR_NO_ELIGIBLE_USERS,
+  ERROR_MAXIMUM_USERS_REACHED,
+};
+
+// Interface for ash client (e.g. Chrome) to set session info for ash.
+interface SessionController {
+  // Sets the client interface.
+  SetClient(SessionControllerClient client);
+
+  // Sets the maximum possible number of logged in users.
+  SetMaxUsers(uint32 max_users);
+
+  // Sets whether the screen can be locked.
+  SetCanLockScreen(bool can_lock);
+
+  // Sets whether the screen should be locked automatically before suspending.
+  SetShouldLockScreenAutomatically(bool should_lock);
+
+  // Sets whether adding a user to session is allowed.
+  SetAddUserSessionPolicy(AddUserSessionPolicy add_user_session_policy);
+
+  // Sets the current state of the ash session.
+  SetSessionState(SessionState session_state);

[James Cook, 2016/12/01 23:01:43]

If all of the above functions are going to be called each time the session state
changes, should SetSessionState() take a list of args with all the data from the
functions above? Right now I think it does 6 IPCs whenever any one thing
changes.

[xiyuan, 2016/12/06 00:46:34]

Makes sense. I was thinking keeping them separate so that we could update them
individually. But the impl currently updates all of them when user signs in so
does not make sense to make separate calls. Combined them into one call.

+
+  // Sets the list of user sessions. This list is taken as LRU sorted with
+  // the first being the currently active user session.
+  SetUserSessions(array<UserSession> user_sessions);

[James Cook, 2016/12/01 23:01:43]

Is this going to be re-sent every time the order of the list changes? If so it's
going to ship serialized bitmaps across IPC each time. Maybe the avatar bitmaps
should be taken out of UserSession and sent separately?

EDIT: I see http://crbug.com/670422 - maybe reference that here and/or in struct
UserSession above? But my comment might be a little different -- in addition to
watching for changes to the image it would be nice not to re-send the bitmap
when the list is reordered. You might want to add that to the bug. I'm OK with
fixing this in a follow-up CL.

[xiyuan, 2016/12/06 00:46:34]

Good point. I overlooked this.

Split SetUserSessions into two calls: UpdateUserSession and SetUserSessionOrder.
The first is called when a user session is added and would used later to update
user meta changes such as avatar change. The 2nd one sends the a list of session
ids to order the user sessions in ash.

+};
+
+// 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).

[James Cook, 2016/12/01 23:01:43]

nit: wrap with line above

[xiyuan, 2016/12/06 00:46:34]

Done.

+  SwitchActiveUser(string account_id);
+
+  // Switch the active user to the next or previous user.
+  CycleActiveUser(bool next_user);
+};