Importance slider logging.

Change-Id: I3c4ad73d1460e4d28cb1a10846159128590d2b20
diff --git a/proto/src/metrics_constants.proto b/proto/src/metrics_constants.proto
index 439be81..3f3f851 100644
--- a/proto/src/metrics_constants.proto
+++ b/proto/src/metrics_constants.proto
@@ -362,5 +362,12 @@
 
     // Logged when a user dismisses a task in overview
     OVERVIEW_DISMISS = 289;
+
+    // Logged when the user modifying the notification importance slider.
+    ACTION_MODIFY_IMPORTANCE_SLIDER = 290;
+
+    // Logged when the user saves a modification to notification importance. Negative numbers
+    // indicate the user lowered the importance; positive means they increased it.
+    ACTION_SAVE_IMPORTANCE = 291;
   }
 }