It'd be good to do this in views-based lock. IMO not worth the effort in webui-based lock.

Move to M63

I did some time logging here after the work in issue 746657. After LockStateController::LockWithoutAnimation() call, session_controller will LockScreen. It is an async call. It takes around 400ms~1000ms until OnLockStateChanged is received. Then it will do a post lock animation for lock screen containers, which takes 350ms.

Question: do we have to wait OnLockStateChanged in the reporter's case? Considering it must lock the screen with "Show lock screen when waking from sleep" setting enabled.

OnLockStateChanged is triggered by SetSessionState(LOCKED) in ScreenLocker::ScreenLockReady [1]. For webui lock screen, this is called when lock screen window is created and the JS calls back. This is as a way to ensure there is a usable lock screen. If anything goes wrong, the LockStateController would time out and terminate the session.

The delay to OnLockStateChanged is long probably due to the complicated logic in webui. It should be improved with views backed lock screen.
 

[1]: https://cs.chromium.org/chromium/src/chrome/browser/chromeos/login/lock/screen_locker.cc?rcl=668ae80f58beaeb2852cd1d6d0609cbe0f3d7a7f&l=633

Thanks xiyuan. I will work on eliminating the 350ms post lock animation first in this bug.

The following revision refers to this bug:
  https://chromium.googlesource.com/chromium/src.git/+/f721f259f771dab64ef5c7be0ee8b97961fd8e70

commit f721f259f771dab64ef5c7be0ee8b97961fd8e70
Author: Qiang Xu <warx@chromium.org>
Date: Fri Sep 01 06:56:05 2017

cros: immediate post lock animation for screen off locking animation

changes:
- Using |post_lock_immediate_animation_|, which is set to true in
LockWithoutAnimation and reset to false in PostLockAnimationFinished. I
think it is sufficient. The other case like if locking screen fails,
Chrome will just crash it.
- Modify tests to test more details.

tablet power button is 0 ms, while regular locking is still ~350ms.

Test: test coverage. Tested on device that post lock animation time for
Bug:  748732 
Change-Id: I0f7c7a8a109c3176ed7b31b9f710839dec243c6e
Reviewed-on: https://chromium-review.googlesource.com/646833
Commit-Queue: Qiang(Joe) Xu <warx@chromium.org>
Reviewed-by: Dan Erat (OOO Fri-Mon) <derat@chromium.org>
Cr-Commit-Position: refs/heads/master@{#499146}
[modify] https://crrev.com/f721f259f771dab64ef5c7be0ee8b97961fd8e70/ash/system/power/power_event_observer_unittest.cc
[modify] https://crrev.com/f721f259f771dab64ef5c7be0ee8b97961fd8e70/ash/system/power/tablet_power_button_controller_unittest.cc
[modify] https://crrev.com/f721f259f771dab64ef5c7be0ee8b97961fd8e70/ash/wm/lock_state_controller.cc
[modify] https://crrev.com/f721f259f771dab64ef5c7be0ee8b97961fd8e70/ash/wm/lock_state_controller.h