Add a test of updating cached height for popup notifications

ash/system/web_notification/web_notification_tray.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_SYSTEM_WEB_NOTIFICATION_WEB_NOTIFICATION_TRAY_H_
 #define ASH_SYSTEM_WEB_NOTIFICATION_WEB_NOTIFICATION_TRAY_H_
 
 #include <memory>
 
 #include "ash/ash_export.h"
@@ skipping 43 matching lines @@
       public ui::SimpleMenuModel::Delegate {
  public:
   explicit WebNotificationTray(StatusAreaWidget* status_area_widget);
   ~WebNotificationTray() override;
 
   // Sets the height of the system tray from the edge of the work area so that
   // the notification popups don't overlap with the tray. Passes 0 if no UI is
   // shown in the system tray side.
   void SetSystemTrayHeight(int height);
 
+  // Returns the current system tray height.
+  int system_tray_height_for_test() const;
+
   // Returns true if it should block the auto hide behavior of the shelf.
   bool ShouldBlockShelfAutoHide() const;
 
   // Returns true if the message center bubble is visible.
   bool IsMessageCenterBubbleVisible() const;
 
   // Returns true if the mouse is inside the notification bubble.
   bool IsMouseInNotificationBubble() const;
 
   // Shows the message center bubble.
@@ skipping 100 matching lines @@
   bool should_block_shelf_auto_hide_;
 
   std::unique_ptr<AshPopupAlignmentDelegate> popup_alignment_delegate_;
 
   DISALLOW_COPY_AND_ASSIGN(WebNotificationTray);
 };
 
 }  // namespace ash
 
 #endif  // ASH_SYSTEM_WEB_NOTIFICATION_WEB_NOTIFICATION_TRAY_H_