Add a test of updating cached height for popup notifications

ash/system/web_notification/ash_popup_alignment_delegate.h

 // Copyright 2014 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_ASH_POPUP_ALIGNMENT_DELEGATE_H_
 #define ASH_SYSTEM_WEB_NOTIFICATION_ASH_POPUP_ALIGNMENT_DELEGATE_H_
 
 #include <stdint.h>
 
 #include "ash/ash_export.h"
@@ skipping 30 matching lines @@
   explicit AshPopupAlignmentDelegate(ShelfLayoutManager* shelf);
   ~AshPopupAlignmentDelegate() override;
 
   // Start observing the system.
   void StartObserving(display::Screen* screen, const display::Display& display);
 
   // Sets the current height of the system tray so that the notification toasts
   // can avoid it.
   void SetSystemTrayHeight(int height);
 
+  // Returns the current system tray height.
+  int system_tray_height_for_test() const { return system_tray_height_; }
+
   // Overridden from message_center::PopupAlignmentDelegate:
   int GetToastOriginX(const gfx::Rect& toast_bounds) const override;
   int GetBaseLine() const override;
   int GetWorkAreaBottom() const override;
   bool IsTopDown() const override;
   bool IsFromLeft() const override;
   void RecomputeAlignment(const display::Display& display) override;
 
  private:
   friend class AshPopupAlignmentDelegateTest;
@@ skipping 25 matching lines @@
   gfx::Rect work_area_;
   ShelfLayoutManager* shelf_;
   int system_tray_height_;
 
   DISALLOW_COPY_AND_ASSIGN(AshPopupAlignmentDelegate);
 };
 
 }  // namespace ash
 
 #endif  // ASH_SYSTEM_WEB_NOTIFICATION_ASH_POPUP_ALIGNMENT_DELEGATE_H_