Support hit object pooling scrolling playfield

osu.Game/Rulesets/UI/Scrolling/ScrollingPlayfield.cs

@@ -24,6 +24,12 @@ namespace osu.Game.Rulesets.UI.Scrolling
             Direction.BindTo(ScrollingInfo.Direction);
         }
 
+        protected override void OnNewDrawableHitObject(DrawableHitObject drawableHitObject)
+        {
+            drawableHitObject.HitObjectApplied +=
+                ((ScrollingHitObjectContainer)HitObjectContainer).InvalidateDrawableHitObject;
+        }
+
         /// <summary>
         /// Given a position in screen space, return the time within this column.
         /// </summary>