Add SessionStateObserver with ActiveUserChanged()

ash/system/tray/system_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_TRAY_SYSTEM_TRAY_H_
 #define ASH_SYSTEM_TRAY_SYSTEM_TRAY_H_
 
 #include "ash/ash_export.h"
 #include "ash/system/tray/system_tray_bubble.h"
 #include "ash/system/tray/tray_background_view.h"
@@ skipping 106 matching lines @@
 
   // Returns a pointer to the system bubble or NULL if none.
   internal::SystemTrayBubble* GetSystemBubble();
 
   // Returns true if any bubble is visible.
   bool IsAnyBubbleVisible() const;
 
   // Returns true if the mouse is inside the notification bubble.
   bool IsMouseInNotificationBubble() const;
 
+  // Closes system bubble and returns true if it did exist.
+  bool CloseSystemBubble() const;
+
   // Accessors for testing.
 
   // Returns true if the bubble exists.
-  bool CloseSystemBubbleForTest() const;
   bool CloseNotificationBubbleForTest() const;
 
   // Overridden from TrayBackgroundView.
   virtual void SetShelfAlignment(ShelfAlignment alignment) OVERRIDE;
   virtual void AnchorUpdated() OVERRIDE;
   virtual base::string16 GetAccessibleNameForTray() OVERRIDE;
   virtual void HideBubbleWithView(
       const views::TrayBubbleView* bubble_view) OVERRIDE;
   virtual bool ClickedOutsideBubble() OVERRIDE;
 
@@ skipping 72 matching lines @@
   bool hide_notifications_;
 
   internal::TrayAccessibility* tray_accessibility_;  // not owned
 
   DISALLOW_COPY_AND_ASSIGN(SystemTray);
 };
 
 }  // namespace ash
 
 #endif  // ASH_SYSTEM_TRAY_SYSTEM_TRAY_H_