Add TrayLocale for locale change notifications.

ash/system/tray/system_tray.h

Index: ash/system/tray/system_tray.h
diff --git a/ash/system/tray/system_tray.h b/ash/system/tray/system_tray.h
index 24e8257e3ef94eaddda38f23ea5fc1d267c9417d..f2f385d0878be4f51eef842440e62c3f12d0729c 100644
--- a/ash/system/tray/system_tray.h
+++ b/ash/system/tray/system_tray.h
@@ -29,6 +29,7 @@ class CapsLockObserver;
 class ClockObserver;
 class DriveObserver;
 class IMEObserver;
+class LocaleObserver;
 class NetworkObserver;
 class PowerStatusObserver;
 class UpdateObserver;
@@ -126,6 +127,9 @@ class ASH_EXPORT SystemTray : public internal::ActionableView,
   IMEObserver* ime_observer() const {
     return ime_observer_;
   }
+  LocaleObserver* locale_observer() const {
+    return locale_observer_;
+  }
   NetworkObserver* network_observer() const {
     return network_observer_;
   }
@@ -209,6 +213,7 @@ class ASH_EXPORT SystemTray : public internal::ActionableView,
   ClockObserver* clock_observer_;
   DriveObserver* drive_observer_;
   IMEObserver* ime_observer_;
+  LocaleObserver* locale_observer_;
   NetworkObserver* network_observer_;
   PowerStatusObserver* power_status_observer_;
   UpdateObserver* update_observer_;