Add Unseen state to Reading List Entry

components/reading_list/ios/proto/reading_list.proto

 // Copyright 2016 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 //
 // Sync protocol datatype extension for the reading list items.
 
 syntax = "proto2";
 
 option optimize_for = LITE_RUNTIME;
 
 package reading_list;
 
 // Local Reading list entry. This proto contains the fields stored locally for
 // a reading list entry. It must be kept synced with the
 // sync_pb.ReadingListSpecifics protobuf.
 message ReadingListLocal {
   optional string entry_id = 1;
   optional string title = 2;
   optional string url = 3;
   optional int64 creation_time_us = 4;
   optional int64 update_time_us = 5;
   optional int64 first_read_time_us = 11;
 
   enum ReadingListEntryStatus {
     UNREAD = 0;
     READ = 1;
+    UNSEEN = 2;
   }
-
+  // If the field is not present, it defaults to UNSEEN.
   optional ReadingListEntryStatus status = 6;
 
   enum DistillationState {
     WAITING = 0;
     PROCESSING = 1;
     PROCESSED = 2;
     WILL_RETRY = 3;
     ERROR = 4;
   }
   optional DistillationState distillation_state = 7;
   optional string distilled_path = 8;
   optional int64 failed_download_counter = 9;
   optional string backoff = 10;
 }