CrOS Shelf: Fix an oversight of my previous CL 1860838

That CL had removed the line that is being re-added here, causing the
|home_launcher_animation_state_| field to never get updated.

TBR=newcomer@chromium.org

Bug: 1006013, 1012353, 1013737, 1015995, 1012760
Change-Id: I489a4df984b2221b299a2bc31692b2ce38b9730a
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1873725Reviewed-by: Manu Cornet <manucornet@chromium.org>
Commit-Queue: Manu Cornet <manucornet@chromium.org>
Cr-Commit-Position: refs/heads/master@{#708159}

ash/shelf/shelf_layout_manager.cc

@@ -850,6 +850,7 @@ void ShelfLayoutManager::OnHomeLauncherTargetPositionChanged(
     return;
   }
 
+  home_launcher_animation_state_ = new_animation_state;
   UpdateVisibilityState();
   MaybeUpdateShelfBackground(AnimationChangeType::IMMEDIATE);
 }