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 64%
copy from components/sync/protocol/reading_list_specifics.proto
copy to ios/chrome/browser/reading_list/proto/reading_list.proto
index 849e57c116c45555639dd857f1267757c153ae1f..59a3a9f7878f187763322040f98dee516ca24f02 100644
--- a/components/sync/protocol/reading_list_specifics.proto
+++ b/ios/chrome/browser/reading_list/proto/reading_list.proto
@@ -8,10 +8,10 @@ syntax = "proto2";
 
 option optimize_for = LITE_RUNTIME;
 
-package sync_pb;
+package reading_list;
 
-// Properties of Reading list items.
-message ReadingListSpecifics {
+// Local Reading list entry.
+message ReadingListLocal {
   optional string entry_id = 1;
 
   optional string title = 2;
@@ -28,4 +28,15 @@ 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 string backoff = 9;
 }