So, what's the specific time we prefer for animation fade in and fade out?

Per Sebastien's comment, I think we should try 250 ms for both directions to start out with -- you said that we're currently using 500 ms for both, right?

(I suspect that we may want a shorter duration for dismissing it, but we'll see.)

yes, we are using 500ms for both currently. Ok, I will change both of them to 250ms first and let's see how it looks like.

The following revision refers to this bug:
  https://chromium.googlesource.com/chromium/src.git/+/afe2cfbc5e765aa82a7aece9c2bbe41851e53e18

commit afe2cfbc5e765aa82a7aece9c2bbe41851e53e18
Author: Min Chen <minch@google.com>
Date: Thu Mar 29 21:35:19 2018

ash: Make power button menu animation faster.

Bug:  826063 
Change-Id: I1930da3effd7952d2019e480048778075a0bcd58
Reviewed-on: https://chromium-review.googlesource.com/981686
Commit-Queue: Min Chen <minch@chromium.org>
Reviewed-by: Dan Erat <derat@chromium.org>
Reviewed-by: Qiang Xu <warx@google.com>
Cr-Commit-Position: refs/heads/master@{#546960}
[modify] https://crrev.com/afe2cfbc5e765aa82a7aece9c2bbe41851e53e18/ash/system/power/power_button_menu_screen_view.cc
[modify] https://crrev.com/afe2cfbc5e765aa82a7aece9c2bbe41851e53e18/ash/system/power/power_button_menu_view.cc
[modify] https://crrev.com/afe2cfbc5e765aa82a7aece9c2bbe41851e53e18/ash/system/power/power_button_menu_view.h

The following revision refers to this bug:
  https://chromium.googlesource.com/chromium/src.git/+/85896467ff7cfd878ffc039220fb13184445684b

commit 85896467ff7cfd878ffc039220fb13184445684b
Author: Peter Mayo <petermayo@chromium.org>
Date: Thu Mar 29 22:22:30 2018

Revert "ash: Make power button menu animation faster."

This reverts commit afe2cfbc5e765aa82a7aece9c2bbe41851e53e18.

Reason for revert: compile fail on linux-chromeos-dbg

Original change's description:
> ash: Make power button menu animation faster.
> 
> Bug:  826063 
> Change-Id: I1930da3effd7952d2019e480048778075a0bcd58
> Reviewed-on: https://chromium-review.googlesource.com/981686
> Commit-Queue: Min Chen <minch@chromium.org>
> Reviewed-by: Dan Erat <derat@chromium.org>
> Reviewed-by: Qiang Xu <warx@google.com>
> Cr-Commit-Position: refs/heads/master@{#546960}

TBR=derat@chromium.org,minch@chromium.org,warx@google.com

Change-Id: I1e1e7937ce2ff174c37f96ef50370d464bdfe86a
No-Presubmit: true
No-Tree-Checks: true
No-Try: true
Bug:  826063 
Reviewed-on: https://chromium-review.googlesource.com/986724
Reviewed-by: Peter Mayo <petermayo@chromium.org>
Commit-Queue: Peter Mayo <petermayo@chromium.org>
Cr-Commit-Position: refs/heads/master@{#546980}
[modify] https://crrev.com/85896467ff7cfd878ffc039220fb13184445684b/ash/system/power/power_button_menu_screen_view.cc
[modify] https://crrev.com/85896467ff7cfd878ffc039220fb13184445684b/ash/system/power/power_button_menu_view.cc
[modify] https://crrev.com/85896467ff7cfd878ffc039220fb13184445684b/ash/system/power/power_button_menu_view.h

The following revision refers to this bug:
  https://chromium.googlesource.com/chromium/src.git/+/a8e632222551c06bd4c5927687cf7fc261e5690b

commit a8e632222551c06bd4c5927687cf7fc261e5690b
Author: Min Chen <minch@google.com>
Date: Fri Mar 30 16:33:40 2018

[reland]ash: Make power button menu animation faster.

Bug:  826063 
Change-Id: I6ba335fc31bdc87d2c0d8d6ac8dbdfbc84df7ad2
Reviewed-on: https://chromium-review.googlesource.com/987211
Reviewed-by: Dan Erat <derat@chromium.org>
Reviewed-by: Qiang Xu <warx@google.com>
Commit-Queue: Min Chen <minch@chromium.org>
Cr-Commit-Position: refs/heads/master@{#547181}
[modify] https://crrev.com/a8e632222551c06bd4c5927687cf7fc261e5690b/ash/system/power/power_button_menu_screen_view.cc
[modify] https://crrev.com/a8e632222551c06bd4c5927687cf7fc261e5690b/ash/system/power/power_button_menu_view.cc
[modify] https://crrev.com/a8e632222551c06bd4c5927687cf7fc261e5690b/ash/system/power/power_button_menu_view.h