Create a strict order in ReadingListSpecifics

components/reading_list/ios/reading_list_model_impl.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_model_impl.h"
 
 #include "base/bind.h"
 #include "base/logging.h"
 #include "base/memory/ptr_util.h"
 #include "base/strings/string_util.h"
@@ skipping 134 matching lines @@
     observer.ReadingListDidApplyChanges(this);
   }
 }
 
 ReadingListEntry* ReadingListModelImpl::SyncMergeEntry(
     std::unique_ptr<ReadingListEntry> entry) {
   DCHECK(CalledOnValidThread());
   DCHECK(loaded());
   ReadingListEntry* existing_entry = GetMutableEntryFromURL(entry->URL());
   DCHECK(existing_entry);
-  DCHECK(existing_entry->UpdateTime() < entry->UpdateTime());
-
   GURL url = entry->URL();
 
   for (auto& observer : observers_)
     observer.ReadingListWillMoveEntry(this, url);
 
   if (existing_entry->IsRead()) {
     read_entry_count_--;
   } else {
     unread_entry_count_--;
   }
-  // Merge local data in new entry.
-  entry->MergeLocalStateFrom(*existing_entry);
-
-  entries_->find(url)->second = std::move(*entry);
+  existing_entry->MergeWithEntry(*entry);
 
   existing_entry = GetMutableEntryFromURL(url);
   if (existing_entry->IsRead()) {
     read_entry_count_++;
   } else {
     unread_entry_count_++;
   }
   for (auto& observer : observers_)
     observer.ReadingListDidApplyChanges(this);
   return existing_entry;
@@ skipping 223 matching lines @@
 syncer::ModelTypeSyncBridge* ReadingListModelImpl::GetModelTypeSyncBridge() {
   DCHECK(loaded());
   if (!storage_layer_)
     return nullptr;
   return storage_layer_->GetModelTypeSyncBridge();
 }
 
 ReadingListModelStorage* ReadingListModelImpl::StorageLayer() {
   return storage_layer_.get();
 }