Reading List create protobuf store

ios/chrome/browser/reading_list/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;
+
+import "reading_list_specifics.proto";
+
+package reading_list;
+
+// Local Reading list entry.
+message ReadingListLocal {
+  optional sync_pb.ReadingListSpecifics entry = 1;
+  enum DistillationState {
+    WAITING = 0;
+    PROCESSING = 1;
+    PROCESSED = 2;
+    WILL_RETRY = 3;
+    ERROR = 4;
+  }
+  optional DistillationState distillation_state = 2;
+  optional string distilled_url = 3;
+  optional string backoff = 4;
+}