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 fb898318e2b5081c4a43f1bfa9028289ab6243ea..fec24ce538b1e039d2b69cc98e34cfe3e9baf1b1 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);
 
   // Pops up the detailed view for this item. An item can request to show its
   // detailed view using this function (e.g. from an observer callback when
@@ -70,6 +71,9 @@ 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();