Add SystemTrayObservers

ash/system/tray/system_tray_delegate.h

Index: ash/system/tray/system_tray_delegate.h
diff --git a/ash/system/tray/system_tray_delegate.h b/ash/system/tray/system_tray_delegate.h
index b8c7f3e0268cb4329051d8b8f9c3ae59f697fa24..9f9f220228fb67c0e01299e58ab22d0630ad83ec 100644
--- a/ash/system/tray/system_tray_delegate.h
+++ b/ash/system/tray/system_tray_delegate.h
@@ -9,6 +9,7 @@
 #include <vector>
 
 #include "ash/ash_export.h"
+#include "ash/system/locale/locale_observer.h"
 #include "ash/system/power/power_supply_status.h"
 #include "ash/system/user/login_status.h"
 #include "base/file_path.h"
@@ -19,6 +20,8 @@
 
 namespace ash {
 
+class SystemTrayObservers;
+
 struct ASH_EXPORT NetworkIconInfo {
   NetworkIconInfo();
   ~NetworkIconInfo();
@@ -107,6 +110,9 @@ class SystemTrayDelegate {
   // Called after SystemTray has been instantiated.
   virtual void Initialize() = 0;
 
+  // Returns a SystemTrayObservers, or NULL of observers are not implemented.
+  virtual SystemTrayObservers* GetSystemTrayObservers() = 0;
+
   // Returns true if system tray should be visible on startup.
   virtual bool GetTrayVisibilityOnStartup() = 0;