add rank to notification visibility log

Only sysui knows the true rank, since it can (and does) reorder things.
The visibility logs are down in the service because it has other bits of data.

Bug: 21395744
Change-Id: Ibf9479dc2306fb27fb5df3bf21e161478d36d587
diff --git a/services/core/java/com/android/server/EventLogTags.logtags b/services/core/java/com/android/server/EventLogTags.logtags
index 49d4c22..43b640b 100644
--- a/services/core/java/com/android/server/EventLogTags.logtags
+++ b/services/core/java/com/android/server/EventLogTags.logtags
@@ -74,7 +74,7 @@
 # when a notification has been canceled
 27530 notification_canceled (key|3),(reason|1),(lifespan|1),(freshness|1),(exposure|1)
 # replaces 27510 with a row per notification
-27531 notification_visibility (key|3),(visibile|1),(lifespan|1),(freshness|1)
+27531 notification_visibility (key|3),(visibile|1),(lifespan|1),(freshness|1),(exposure|1),(rank|1)
 # a notification emited noise, vibration, or light
 27532 notification_alert (key|3),(buzz|1),(beep|1),(blink|1)