Add new subreason for kernel out-of-memory kills

Test: build
Bug: 244232958
Change-Id: Idfa4fd0b763a97d6c5e6615418bf68c92b3eaf7d
diff --git a/stats/enums/app/enums.proto b/stats/enums/app/enums.proto
index a447365..1fd2dbe 100644
--- a/stats/enums/app/enums.proto
+++ b/stats/enums/app/enums.proto
@@ -574,6 +574,12 @@
      * The process was killed because the binder proxy limit for system server was exceeded.
      */
      SUBREASON_EXCESSIVE_BINDER_OBJECTS = 29;
+
+    /**
+     * The process was killed by the [kernel] Out-of-memory (OOM) killer; this
+     * would be set only when the reason is {@link #REASON_LOW_MEMORY}.
+     */
+    SUBREASON_OOM_KILL = 30;
 }
 
 /**