Add Store+Sync to reading list.

ios/chrome/browser/reading_list/proto/reading_list.proto

Index: ios/chrome/browser/reading_list/proto/reading_list.proto
diff --git a/components/sync/protocol/reading_list_specifics.proto b/ios/chrome/browser/reading_list/proto/reading_list.proto
similarity index 52%
copy from components/sync/protocol/reading_list_specifics.proto
copy to ios/chrome/browser/reading_list/proto/reading_list.proto
index 849e57c116c45555639dd857f1267757c153ae1f..c7b514d893255afc6aa54aafd22c6b5353107d71 100644
--- a/components/sync/protocol/reading_list_specifics.proto
+++ b/ios/chrome/browser/reading_list/proto/reading_list.proto
@@ -8,10 +8,12 @@ syntax = "proto2";
 
 option optimize_for = LITE_RUNTIME;
 
-package sync_pb;
+package reading_list;
 
-// Properties of Reading list items.
-message ReadingListSpecifics {
+// 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;
@@ -28,4 +30,16 @@ message ReadingListSpecifics {
   }
 
   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_url = 8;
+  optional int64 failed_download_counter = 9;
+  optional string backoff = 10;
 }