add reserved latency field

Bug: 65724609
Test: make
Change-Id: I9bc8d9bf6818c93cd21c02962d93ab1193d56fc9
diff --git a/proto/src/metrics_constants.proto b/proto/src/metrics_constants.proto
index d89cc96..e3be5d4 100644
--- a/proto/src/metrics_constants.proto
+++ b/proto/src/metrics_constants.proto
@@ -5503,6 +5503,10 @@
     // OS: P
     ACTION_MANAGE_NOTIFICATIONS = 1358;
 
+    // This value should never appear in log outputs - it is reserved for
+    // internal platform metrics use.
+    RESERVED_FOR_LOGBUILDER_LATENCY_MILLIS = 1359;
+
     // ---- End P Constants, all P constants go above this line ----
     // Add new aosp constants above this line.
     // END OF AOSP CONSTANTS