chromeos: Refactor system tray code into PowerStatus.

ash/system/chromeos/settings/tray_settings.h

Index: ash/system/chromeos/settings/tray_settings.h
diff --git a/ash/system/chromeos/settings/tray_settings.h b/ash/system/chromeos/settings/tray_settings.h
index daa29cf8b6455c0f6227399e765852a8456f3778..e48aad3b55dc9162b9008096a15e3bedeecea97a 100644
--- a/ash/system/chromeos/settings/tray_settings.h
+++ b/ash/system/chromeos/settings/tray_settings.h
@@ -5,7 +5,6 @@
 #ifndef ASH_SYSTEM_CHROMEOS_SETTINGS_TRAY_SETTINGS_H_
 #define ASH_SYSTEM_CHROMEOS_SETTINGS_TRAY_SETTINGS_H_
 
-#include "ash/system/chromeos/power/power_status.h"
 #include "ash/system/tray/system_tray_item.h"
 
 namespace ash {
@@ -15,7 +14,7 @@ namespace tray {
 class SettingsDefaultView;
 }
 
-class TraySettings : public SystemTrayItem, public PowerStatus::Observer {
+class TraySettings : public SystemTrayItem {
  public:
   explicit TraySettings(SystemTray* system_tray);
   virtual ~TraySettings();
@@ -30,10 +29,6 @@ class TraySettings : public SystemTrayItem, public PowerStatus::Observer {
   virtual void DestroyDetailedView() OVERRIDE;
   virtual void UpdateAfterLoginStatusChange(user::LoginStatus status) OVERRIDE;
 
-  // Overridden from PowerStatus::Observer.
-  virtual void OnPowerStatusChanged(
-      const chromeos::PowerSupplyStatus& status) OVERRIDE;
-
   tray::SettingsDefaultView* default_view_;
 
   DISALLOW_COPY_AND_ASSIGN(TraySettings);