Introduces CONTAINER_WIDGETS_TRAY to LauncherSettings.Favorites.

This would log LAUNCHER_ITEM_DRAG_STARTED event when an item is dragged from widgets tray. This also fixes empty component with widget logs.

Sample Log: https://docs.google.com/document/d/1CBP2yTcXdFhPdNG5ZmWFKSgd8mDbMevY-akVlUXPLDo/edit#bookmark=id.bk5w3n8uwhcl

Bug: 152978018
Change-Id: I51d16edae13973d5e62adda0e4efa861fa10dc1b
diff --git a/protos/launcher_atom.proto b/protos/launcher_atom.proto
index f1b71e8..f1db144 100644
--- a/protos/launcher_atom.proto
+++ b/protos/launcher_atom.proto
@@ -48,12 +48,16 @@
     HotseatContainer hotseat = 2;
     FolderContainer folder = 3;
     AllAppsContainer all_apps_container = 4;
+    WidgetsContainer widgets_container = 5;
   }
 }
 
 message AllAppsContainer {
 }
 
+message WidgetsContainer {
+}
+
 enum Origin {
   UNKNOWN = 0;
   DEFAULT_LAYOUT = 1;       // icon automatically placed in workspace, folder, hotseat