Use mojo SystemTray interfaces for both mash and classic ash

ash/common/system/tray/system_tray_notifier.h

Index: ash/common/system/tray/system_tray_notifier.h
diff --git a/ash/common/system/tray/system_tray_notifier.h b/ash/common/system/tray/system_tray_notifier.h
index 29bb9f521061c39977d5f613cee9636c32ef3d10..f3fb7d34b27dd7d1930fbf0f1eedcc32d9826da7 100644
--- a/ash/common/system/tray/system_tray_notifier.h
+++ b/ash/common/system/tray/system_tray_notifier.h
@@ -65,10 +65,11 @@ class ASH_EXPORT SystemTrayNotifier {
   void NotifyAudioActiveInputNodeChanged();
 
   // Date and time.
-  void AddClockObserver(ClockObserver* observer);
-  void RemoveClockObserver(ClockObserver* observer);
+  // TODO: Remove all these in favor of SystemTrayController.
+  //void AddClockObserver(ClockObserver* observer);
+  //void RemoveClockObserver(ClockObserver* observer);
   void NotifyRefreshClock();
-  void NotifyDateFormatChanged();
+  // void NotifyDateFormatChanged();
   void NotifySystemClockTimeUpdated();
   void NotifySystemClockCanSetTimeChanged(bool can_set_time);