Only update system power indicators on change

ash/system/power/power_status_view.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_POWER_POWER_STATUS_VIEW_H_
 #define ASH_SYSTEM_POWER_POWER_STATUS_VIEW_H_
 
 #include "ash/system/power/power_supply_status.h"
 #include "ui/views/view.h"
 
@@ skipping 29 matching lines @@
   void UpdateTextForDefaultView();
   void UpdateTextForNotificationView();
 
   // Overridden from views::View.
   virtual void ChildPreferredSizeChanged(views::View* child) OVERRIDE;
 
   // Layout default view UI items on the right side of system tray pop up item
   // if true; otherwise, layout the UI items on the left side.
   bool default_view_right_align_;
 
-  // labels used only for VIEW_NOTIFICATION.
+  // Labels used only for VIEW_NOTIFICATION.
   views::Label* status_label_;
   views::Label* time_label_;
 
-  // labels used only for VIEW_DEFAULT.
+  // Labels used only for VIEW_DEFAULT.
   views::Label* time_status_label_;
 
+  // Battery status indicator icon.
   views::ImageView* icon_;
+
+  // Index of the current icon in the icon array image, or -1 if unknown.
+  int icon_image_index_;
+
   ViewType view_type_;
 
   PowerSupplyStatus supply_status_;
 
   DISALLOW_COPY_AND_ASSIGN(PowerStatusView);
 };
 
 }  // namespace internal
 }  // namespace ash
 
 #endif  // ASH_SYSTEM_POWER_POWER_STATUS_VIEW_H_