Adds additional folder label states (UNLABELED & EMPTY_LABEL)

UNLABELED -> title==null and EMPTY_LABEL -> title=="". When adding new items for the folder if the folder is in UNLABELED state, auto-labeling will be enabled.
This change also addresses auto-labeling issue due to false edit from UNLABELED to EMPTY.

Bug: 159164315

Change-Id: Ia17cd27b4afb60420dc15c544f544061fc46ad33
diff --git a/protos/launcher_atom.proto b/protos/launcher_atom.proto
index d1185bd..98ce9af 100644
--- a/protos/launcher_atom.proto
+++ b/protos/launcher_atom.proto
@@ -96,8 +96,21 @@
   ADD_TO_HOMESCREEN = 6;    // play install + launcher home setting
   ALLAPPS_PREDICTION = 7;   // from prediction bar in all apps container
   HOTSEAT_PREDICTION = 8;   // from prediction bar in hotseat container
-  SUGGESTED_LABEL = 9;      // folder icon's label was suggested
-  MANUAL_LABEL = 10;        // folder icon's label was manually edited
+
+  // Folder's label is one of the non-empty suggested values.
+  SUGGESTED_LABEL = 9;
+
+  // Folder's label is non-empty, manually entered by the user
+  // and different from any of suggested values.
+  MANUAL_LABEL = 10;
+
+  // Folder's label is not yet assigned( i.e., title == null).
+  // Eligible for auto-labeling.
+  UNLABELED = 11;
+
+  // Folder's label is empty(i.e., title == "").
+  // Not eligible for auto-labeling.
+  EMPTY_LABEL = 12;
 }
 
 // Main app icons