Reland "Show notification counter even on lock screen"

This reverts commit 3767b2ad.

Reason for revert: This CL is innocent. I fixed the issue separately: crrev.com/c/1297853.

Original change's description:
> Revert "Show notification counter even on lock screen"
>
> This reverts commit 155c0b00.
>
> Reason for revert: This breaks the lock screen notification.
>
> Original change's description:
> > Show notification counter even on lock screen
> >
> > - Unblock notifications in SessionStateNotificationBlocker
> > - Hide the message center by seeing the session sate (previously, it
> >   saw the count of notifications)
> > - Change height below scroll, by checking the visibility of message
> >   center (previously, it checked only the height)
> >
> > Bug: 893945
> > Test: manual
> >
> > Change-Id: I39d30d0949d0f44078193ab7e4859f66eeebf880
> > Reviewed-on: https://chromium-review.googlesource.com/c/1282426
> > Reviewed-by: Tatsuhisa Yamaguchi <yamaguchi@chromium.org>
> > Reviewed-by: Tetsui Ohkubo <tetsui@chromium.org>
> > Commit-Queue: Yoshiki Iguchi <yoshiki@chromium.org>
> > Cr-Commit-Position: refs/heads/master@{#601824}
>
> TBR=yoshiki@chromium.org,yamaguchi@chromium.org,tetsui@chromium.org
>
> Change-Id: I5b2ded9c9f3212ab3cd085a3ea0721e69b6fae45
> No-Presubmit: true
> No-Tree-Checks: true
> No-Try: true
> Bug: 893945
> Reviewed-on: https://chromium-review.googlesource.com/c/1296330
> Reviewed-by: Yoshiki Iguchi <yoshiki@chromium.org>
> Commit-Queue: Yoshiki Iguchi <yoshiki@chromium.org>
> Cr-Commit-Position: refs/heads/master@{#601930}

TBR=yoshiki@chromium.org,yamaguchi@chromium.org,tetsui@chromium.org


Bug: 893945
Change-Id: Iaee3fc6e7dcb996be1406897b07f571991a7e3db
Reviewed-on: https://chromium-review.googlesource.com/c/1301037
Commit-Queue: Yoshiki Iguchi <yoshiki@chromium.org>
Reviewed-by: Yoshiki Iguchi <yoshiki@chromium.org>
Cr-Commit-Position: refs/heads/master@{#603058}

ash/system/message_center/session_state_notification_blocker.cc

@@ -19,9 +19,7 @@ bool CalculateShouldShowNotification() {
   SessionController* const session_controller =
       Shell::Get()->session_controller();
 
-  return !session_controller->IsRunningInAppMode() &&
-         (!session_controller->IsScreenLocked() ||
-          AshMessageCenterLockScreenController::IsEnabled());
+  return !session_controller->IsRunningInAppMode();
 }
 
 bool CalculateShouldShowPopup() {