Add new metric for SMS Mirroring Setting.

Test: N/A, just adding a metric

Bug: 37546615

Change-Id: I6c160f33e423b25ce43215eb01b64dcd1751b00c
diff --git a/proto/src/metrics_constants.proto b/proto/src/metrics_constants.proto
index adcc8eb..87ac46b 100644
--- a/proto/src/metrics_constants.proto
+++ b/proto/src/metrics_constants.proto
@@ -4213,6 +4213,11 @@
     // OS: O MR
     FIELD_SETTINGS_SEARCH_RESULT_ASYNC_RANKING_STATE = 1083;
 
+    // ACTION: Settings > Connected devices > SMS Mirroring
+    // CATEGORY: SETTINGS
+    // OS: O MR
+    ACTION_SETTINGS_SMS_MIRRORING = 1084;
+
     // Add new aosp constants above this line.
     // END OF AOSP CONSTANTS
   }