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

ash/common/system/tray/tray_background_view.cc

 // Copyright (c) 2012 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "ash/common/system/tray/tray_background_view.h"
 
 #include <algorithm>
 
 #include "ash/common/ash_constants.h"
 #include "ash/common/material_design/material_design_controller.h"
@@ skipping 271 matching lines @@
 // TrayBackgroundView
 
 TrayBackgroundView::TrayBackgroundView(WmShelf* wm_shelf)
     // Note the ink drop style is ignored.
     : ActionableView(nullptr, TrayPopupInkDropStyle::FILL_BOUNDS),
       wm_shelf_(wm_shelf),
       tray_container_(NULL),
       shelf_alignment_(SHELF_ALIGNMENT_BOTTOM),
       background_(NULL),
       is_active_(false),
+      separator_visible_(true),
       widget_observer_(new TrayWidgetObserver(this)) {
   DCHECK(wm_shelf_);
   set_notify_enter_exit_on_child(true);
   set_ink_drop_base_color(kShelfInkDropBaseColor);
   set_ink_drop_visible_opacity(kShelfInkDropVisibleOpacity);
 
   tray_container_ = new TrayContainer(shelf_alignment_);
   SetContents(tray_container_);
   tray_event_filter_.reset(new TrayEventFilter);
 
@@ skipping 275 matching lines @@
 void TrayBackgroundView::OnPaintFocus(gfx::Canvas* canvas) {
   gfx::Rect paint_bounds(GetFocusBounds());
   paint_bounds.Inset(2, -2, 3, -2);
   canvas->DrawSolidFocusRect(paint_bounds, kFocusBorderColor);
 }
 
 void TrayBackgroundView::OnPaint(gfx::Canvas* canvas) {
   ActionableView::OnPaint(canvas);
   if (!MaterialDesignController::IsShelfMaterial() ||
       shelf()->GetBackgroundType() ==
-          ShelfBackgroundType::SHELF_BACKGROUND_DEFAULT) {
+          ShelfBackgroundType::SHELF_BACKGROUND_DEFAULT ||
+      !separator_visible_) {
     return;
   }
   //  In the given |canvas|, for a horizontal shelf draw a separator line to the
   //  right or left of the TrayBackgroundView when the system is LTR or RTL
   //  aligned, respectively. For a vertical shelf draw the separator line
   //  underneath the items instead.
   const bool horizontal_shelf = IsHorizontalAlignment(shelf_alignment_);
   const gfx::Rect local_bounds = GetLocalBounds();
   const int height = kTrayItemSize;
   const int x =
@@ skipping 36 matching lines @@
 }
 
 gfx::Rect TrayBackgroundView::GetBackgroundBounds() const {
   gfx::Insets insets = GetBackgroundInsets();
   gfx::Rect bounds = GetLocalBounds();
   bounds.Inset(insets);
   return bounds;
 }
 
 }  // namespace ash