Remove the extra separator appears on the right side of the shelf

ash/common/system/tray/tray_background_view.h

Index: ash/common/system/tray/tray_background_view.h
diff --git a/ash/common/system/tray/tray_background_view.h b/ash/common/system/tray/tray_background_view.h
index e1743361165297bbefad11bac688c14f6b0ee9a2..4656981335646acd779dc1fef92d34526e6f4a36 100644
--- a/ash/common/system/tray/tray_background_view.h
+++ b/ash/common/system/tray/tray_background_view.h
@@ -129,6 +129,9 @@ class ASH_EXPORT TrayBackgroundView : public ActionableView,
   // ShelfBackgroundAnimatorObserver:
   void UpdateShelfItemBackground(int alpha) override;
 
+  // Updates the visibility of this tray's separator.
+  void set_separator_visibility(bool visible) { separator_visible_ = visible; }
+
   // Gets the anchor for bubbles, which is tray_container().
   views::View* GetBubbleAnchor() const;
 
@@ -181,6 +184,10 @@ class ASH_EXPORT TrayBackgroundView : public ActionableView,
   // in non-MD version and how the ink drop ripples behave in MD version.
   bool is_active_;
 
+  // Visibility of this tray's separator which is a line of 1x32px and 4px to
+  // right of tray.
+  bool separator_visible_;
+
   std::unique_ptr<TrayWidgetObserver> widget_observer_;
   std::unique_ptr<TrayEventFilter> tray_event_filter_;