Add TraySms for SMS messages.

ash/system/tray/system_tray_item.h

Index: ash/system/tray/system_tray_item.h
diff --git a/ash/system/tray/system_tray_item.h b/ash/system/tray/system_tray_item.h
index e91bda490dfe2f9e0ba120ab9649983ad2bc9777..56441c4090c75231dde7d9021a39adf972f67f69 100644
--- a/ash/system/tray/system_tray_item.h
+++ b/ash/system/tray/system_tray_item.h
@@ -55,8 +55,9 @@ class ASH_EXPORT SystemTrayItem {
 
   // Updates the tray view (if applicable) when the user's login status changes.
   // It is not necessary the update the default or detailed view, since the
-  // default/detailed popup is closed when login status changes.
-  virtual void UpdateAfterLoginStatusChange(user::LoginStatus status) = 0;
+  // default/detailed popup is closed when login status changes. The default
+  // implementation does nothing.
+  virtual void UpdateAfterLoginStatusChange(user::LoginStatus status);
 
   // Shows the detailed view for this item. If the main popup for the tray is
   // currently visible, then making this call would use the existing window to
@@ -78,6 +79,9 @@ class ASH_EXPORT SystemTrayItem {
   // currently-shown view is for this item.
   void SetDetailedViewCloseDelay(int for_seconds);
 
+  // Hides the detailed view for this item.
+  void HideDetailedView();
+
   // Shows a notification for this item.
   void ShowNotificationView();