Add merge rules for first read time

components/reading_list/ios/reading_list_store.cc

 // 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.
 
 #include "components/reading_list/ios/reading_list_store.h"
 
 #include "base/bind.h"
 #include "base/logging.h"
 #include "base/memory/ptr_util.h"
 #include "components/reading_list/ios/proto/reading_list.pb.h"
@@ skipping 424 matching lines @@
       rhs.update_time_us() < lhs.update_time_us()) {
     return false;
   }
   if (rhs.update_time_us() == lhs.update_time_us()) {
     if ((rhs.status() == sync_pb::ReadingListSpecifics::UNSEEN &&
          lhs.status() != sync_pb::ReadingListSpecifics::UNSEEN) ||
         (rhs.status() == sync_pb::ReadingListSpecifics::UNREAD &&
          lhs.status() == sync_pb::ReadingListSpecifics::READ))
       return false;
   }
+  if (rhs.creation_time_us() == lhs.creation_time_us()) {
+    if (rhs.first_read_time_us() == 0 && lhs.first_read_time_us() != 0) {
+      return false;
+    }
+    if (rhs.first_read_time_us() > lhs.first_read_time_us() &&
+        lhs.first_read_time_us() != 0) {
+      return false;
+    }
+  }
   return true;
 }