Write eventlog entries for notification panel visibility

Change-Id: Ie7e15ed15739cb5f057c900e1cadf90824b2b4ef
diff --git a/services/core/java/com/android/server/EventLogTags.logtags b/services/core/java/com/android/server/EventLogTags.logtags
index 0f78c9b..9768934 100644
--- a/services/core/java/com/android/server/EventLogTags.logtags
+++ b/services/core/java/com/android/server/EventLogTags.logtags
@@ -58,7 +58,11 @@
 2751 notification_cancel (uid|1|5),(pid|1|5),(pkg|3),(id|1|5),(tag|3),(userid|1|5),(required_flags|1),(forbidden_flags|1),(reason|1|5),(listener|3)
 # when someone tries to cancel all of the notifications for a particular package
 2752 notification_cancel_all (uid|1|5),(pid|1|5),(pkg|3),(userid|1|5),(required_flags|1),(forbidden_flags|1),(reason|1|5),(listener|3)
-
+# when the notification panel is shown
+# Note: New tag range starts here since 2753+ have been used below.
+27500 notification_panel_revealed
+# when the notification panel is hidden
+27501 notification_panel_hidden
 
 # ---------------------------
 # Watchdog.java