Add start time to LmkKillOccurred

To accompany Piper cl/222070329 and https://googleplex-android-review.git.corp.google.com/c/platform/system/core/+/5578724

Bug: 119854389
Test: Manual
Change-Id: Ib2af1b66d4649279fdcb97e7cdf8cdb92e361765
diff --git a/cmds/statsd/src/atoms.proto b/cmds/statsd/src/atoms.proto
index c8405a2..3c53c97 100644
--- a/cmds/statsd/src/atoms.proto
+++ b/cmds/statsd/src/atoms.proto
@@ -2018,6 +2018,9 @@
 
     // SWAP
     optional int64 swap_in_bytes = 8;
+
+    // The elapsed real time of start of the process.
+    optional int64 process_start_time_nanos = 9;
 }
 
 /*