Reuse NativeThemeAuraDark for cros tray.

ash/common/system/status_area_widget.h

 // 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.
 
 #ifndef ASH_COMMON_SYSTEM_STATUS_AREA_WIDGET_H_
 #define ASH_COMMON_SYSTEM_STATUS_AREA_WIDGET_H_
 
 #include "ash/ash_export.h"
 #include "ash/common/login_status.h"
 #include "ash/common/shelf/shelf_background_animator_observer.h"
@@ skipping 60 matching lines @@
   bool ShouldShowShelf() const;
 
   // True if any message bubble is shown.
   bool IsMessageBubbleShown() const;
 
   // Notifies child trays, and the |status_area_widget_delegate_| to schedule a
   // paint.
   void SchedulePaint();
 
   // Overridden from views::Widget:
+  const ui::NativeTheme* GetNativeTheme() const override;
   void OnNativeWidgetActivationChanged(bool active) override;
 
   // ShelfBackgroundAnimatorObserver:
   void UpdateShelfItemBackground(int alpha) override;
 
  private:
   void AddSystemTray();
   void AddWebNotificationTray();
 #if defined(OS_CHROMEOS)
   void AddLogoutButtonTray();
@@ skipping 17 matching lines @@
   LoginStatus login_status_;
 
   WmShelf* wm_shelf_;
 
   DISALLOW_COPY_AND_ASSIGN(StatusAreaWidget);
 };
 
 }  // namespace ash
 
 #endif  // ASH_COMMON_SYSTEM_STATUS_AREA_WIDGET_H_