Clean up compatibility code for last_active_time

This code has been here for one year now. It is time to remove it.
It was added in http://crrev.com/c/5071355.

Fixed: 40946710
Change-Id: Ic2aef138b5709dbe6da441f24472c2c86f7d7abc
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/6175029
Reviewed-by: Stefan Kuhne <skuhne@chromium.org>
Reviewed-by: Marc Treib <treib@chromium.org>
Auto-Submit: Gauthier Ambard <gambard@chromium.org>
Commit-Queue: Stefan Kuhne <skuhne@chromium.org>
Cr-Commit-Position: refs/heads/main@{#1406812}

components/sessions/core/session_service_commands.cc

@@ -171,13 +171,6 @@ enum PersistedWindowShowState {
   PERSISTED_SHOW_STATE_END = 8,
 };
 
-// TODO(crbug.com/40946710): Remove this around December 2024. This is part of a
-// workaround added to support the transition from storing the last_active_time
-// as TimeTicks to Time that was added in December 2023. This is the threshold
-// at which we consider that if a tab is so far in the past, it must be a tab
-// serialized with TimeTicks and not Time.
-const base::TimeDelta kLastActiveWorkaroundThreshold = base::Days(366 * 15);
-
 // Assert to ensure PersistedWindowShowState is updated if ui::WindowShowState
 // is changed.
 // TODO(crbug.com/361560784): Investigate and Remove `kEnd`
@@ -802,33 +795,8 @@ void CreateTabsAndWindows(
         }
         SessionTab* tab =
             GetTab(SessionID::FromSerializedValue(payload.tab_id), tabs);
-        base::Time deserialized_time = base::Time::FromDeltaSinceWindowsEpoch(
+        tab->last_active_time = base::Time::FromDeltaSinceWindowsEpoch(
             base::Microseconds(payload.last_active_time));
-
-        if (base::Time::Now() - deserialized_time >
-            kLastActiveWorkaroundThreshold) {
-          // TODO(crbug.com/40946710): Remove this once enough time has passed
-          // (added in December 2023, can be removed after ~1 year). This is a
-          // workaround put in place during the migration from base::TimeTicks
-          // internal representation to microseconds since Windows epoch. As the
-          // origin point may be vastely different, the values stored in the old
-          // format appear as really old when deserialized in the new format. So
-          // checking all value older than 15 years should be a good enough
-          // filter to catch them. If it is a value stored in the old format, it
-          // should be correctly decoded.
-          base::TimeTicks time_tick_value =
-              base::TimeTicks::FromInternalValue(payload.last_active_time);
-          base::TimeDelta delta_since_epoch =
-              time_tick_value - base::TimeTicks::UnixEpoch();
-          base::Time corrected_time =
-              base::Time::UnixEpoch() + delta_since_epoch;
-          if (base::Time::Now() < corrected_time) {
-            // If the correction is giving a time in the future, set it to now.
-            corrected_time = base::Time::Now();
-          }
-          deserialized_time = corrected_time;
-        }
-        tab->last_active_time = deserialized_time;
         break;
       }