Add merge rules for first read time

components/reading_list/ios/reading_list_store.cc

Index: components/reading_list/ios/reading_list_store.cc
diff --git a/components/reading_list/ios/reading_list_store.cc b/components/reading_list/ios/reading_list_store.cc
index 26ebf29b55883cfec96352ba668f9fa526aedac9..beb300bfc62eaab3f59d24a67f8fce7aa37d0485 100644
--- a/components/reading_list/ios/reading_list_store.cc
+++ b/components/reading_list/ios/reading_list_store.cc
@@ -442,5 +442,14 @@ bool ReadingListStore::CompareEntriesForSync(
          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;
 }