GitLab

     animation after 'Power off' item has focused for
     a while after showing.

focus related spec:
https://drive.google.com/file/d/1JNH0ZDknXSvV00C7TeT4xT_rFx48OdZd/view

changes in this cl,
- Set pre_shutdown_timer_ in PowerButtonController to start the cancellable
  pre-shutdown animation after power menu has been shown for 650ms. And remove
  the previous shutdown_timer_ which will start the clean shutdown after
  pressing power button for 3s.

- Add power button menu item focus. Focus on the 'Power off' item after menu is
  shown.

- Since we add the cancellable pre-shutdown animation back in this cl. Add the
  related tests in LockStateControllerTest back which removed in the previous cl
  https://chromium-review.googlesource.com/c/chromium/src/+/916838

- Modify related tests.

Bug: 826064
Change-Id: Ibefb22067f5bd37849eb1b8c3fb3143f5d3b8dc8
Reviewed-on: https://chromium-review.googlesource.com/991398
Commit-Queue: Min Chen <minch@chromium.org>
Reviewed-by: Qiang Xu <warx@google.com>
Reviewed-by: Dan Erat <derat@chromium.org>
Cr-Commit-Position: refs/heads/master@{#547820}