Adding comment to alarmmanagerservice.proto.

Bug: 70621331
Test: N/A
Change-Id: I471a7d2084cf60be8a22753139dfbcfeb001617f
diff --git a/core/proto/android/server/alarmmanagerservice.proto b/core/proto/android/server/alarmmanagerservice.proto
index 87d302e..53b4be4 100644
--- a/core/proto/android/server/alarmmanagerservice.proto
+++ b/core/proto/android/server/alarmmanagerservice.proto
@@ -47,6 +47,8 @@
   // Only valid if is_interactive is false.
   optional int64 time_until_next_non_wakeup_delivery_ms = 11;
 
+  // Can be negative if the non-wakeup alarm time is in the past (non-wakeup
+  // alarms aren't delivered unil the next time the device wakes up).
   optional int64 time_until_next_non_wakeup_alarm_ms = 12;
   optional int64 time_until_next_wakeup_ms = 13;
   optional int64 time_since_last_wakeup_ms = 14;