ToolbarButtons should still handle MouseDown events.

osu.Game/Overlays/ToolbarButton.cs

@@ -127,6 +127,8 @@ namespace osu.Game.Overlays
             Size = new Vector2(WIDTH + (DrawableText.IsVisible ? DrawableText.DrawSize.X : 0), 1);
         }
 
+        protected override bool OnMouseDown(InputState state, MouseDownEventArgs args) => true;
+
         protected override bool OnClick(InputState state)
         {
             Action?.Invoke();