mash: Shell ref clean up for screen lock

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 "components/signin/public/interfaces/account_id.mojom";
 import "ui/gfx/image/mojo/image.mojom";
 
 // Matches session_manager::SessionState.
@@ skipping 126 matching lines @@
   // a user session because ash/chrome does not support that. All users are
   // logged out at the same time.
   UpdateUserSession(UserSession user_session);
 
   // Sets the order of user sessions. The order is keyed by the session id.
   // Currently, session manager set a LRU order with the first one being the
   // active user session.
   SetUserSessionOrder(array<uint32> user_session_ids);
 
   // Runs the pre-lock animation to start locking ash. When the call returns,
   // |locked| == true means that the post-lock animation is finished and ash is

[Tom Sepez, 2017/04/24 20:54:03]

Is this comment still true in light of the new method?

[xiyuan, 2017/04/24 21:08:22]

Added "ash" before "post-lock" animation to clarify. This is only mean for
animations run by ash. The newly added one is the animation done in the webui
following the ash animation. 

The full event chain is something like this:
1. ash: pre lock animation (lift user desktop);
2. chrome: show webui, when init finishes, set session state LOCKED;
3.- ash: post lock animation (raise lock container);
4. chrome: footer bar fade in
5. ash: PowerEventObserver notifies power_manager

It is interleaved with ash and chrome actions. :( The callback of StartLock is
after 3 and chrome uses it to kick start 4. The added code in this CL is to kick
start 5 after 4. 

I wish we could simplify this too...

   // fully locked. Otherwise |locked| is false, which means something is wrong
   // for the lock and ash is not locked. When the call returns with a true
   // |locked|, screen locker runs the post lock jobs such as a11y announcement
   // etc. Invoked by the screen locker during initialization.
   StartLock() => (bool locked);
 
+  // Notifies ash that chrome lock animations are finished. This is the last
+  // event for locking. SessionController forwards it to PowerEventObserver.
+  NotifyChromeLockAnimationsComplete();
+
   // Runs the pre-unlock animation. Invoked by the screen locker before
   // dismissing. When the mojo call returns, screen locker takes that as a
   // signal of finished unlock animation and dismisses itself.
   RunUnlockAnimation() => ();
 
   // Notifies that chrome is terminating.
   NotifyChromeTerminating();
 };
 
 // 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(signin.mojom.AccountId account_id);
 
   // Switch the active user to the next or previous user.
   CycleActiveUser(CycleUserDirection direction);
 };