Create a strict order in ReadingListSpecifics

components/reading_list/ios/reading_list_entry.h

 // 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.
 
 #ifndef COMPONENTS_READING_LIST_IOS_READING_LIST_ENTRY_H_
 #define COMPONENTS_READING_LIST_IOS_READING_LIST_ENTRY_H_
 
 #include <string>
 
 #include "base/files/file_path.h"
@@ skipping 72 matching lines @@
   std::unique_ptr<sync_pb::ReadingListSpecifics> AsReadingListSpecifics() const;
 
   // Created a ReadingListEntry from the protobuf format.
   static std::unique_ptr<ReadingListEntry> FromReadingListLocal(
       const reading_list::ReadingListLocal& pb_entry);
 
   // Created a ReadingListEntry from the protobuf format.
   static std::unique_ptr<ReadingListEntry> FromReadingListSpecifics(
       const sync_pb::ReadingListSpecifics& pb_entry);
 
-  // Merge the local data from |other| to this.
-  // The local fields (distilled_state_, distilled_url_, backoff_,
-  // failed_download_counter_) of |other| are moved to |this| and must not be
-  // used after this call.
-  void MergeLocalStateFrom(ReadingListEntry& other);
+  // Merge |this| and |other| into this.
+  // Local fields are kept from |this|.
+  // If |other.UpdateTime()| >= |this.UpdateTime()|, all fields are copied from

[gambard, 2016/12/07 10:28:49]

"all fields are copied" is misleading: you do not copy the state field (as
explained in the following line). Can you merge the comments? Like:
all fields except |state| are copied from |other|. The state is copied only if
it is not UNSEEN.

+  // |other|.
+  // If one of the state is UNSEEN, the other state is kept.
+  //
+  // After calling |MergeLocalStateFrom|, the result must verify
+  // ReadingListStore.CompareEntriesForSync(old_this.AsReadingListSpecifics(),
+  //                                        new_this.AsReadingListSpecifics())
+  // and
+  // ReadingListStore.CompareEntriesForSync(other.AsReadingListSpecifics(),
+  //                                        new_this.AsReadingListSpecifics()).
+  void MergeWithEntry(const ReadingListEntry& other);
 
   ReadingListEntry& operator=(ReadingListEntry&& other);
 
   bool operator==(const ReadingListEntry& other) const;
 
-  // Returns whether |lhs| is more recent than |rhs|.
-  static bool CompareEntryUpdateTime(const ReadingListEntry& lhs,
-                                     const ReadingListEntry& rhs);
-
   // Sets the title.
   void SetTitle(const std::string& title);
   // Sets the distilled URL and switch the state to PROCESSED and reset the time
   // until the next try.
   void SetDistilledPath(const base::FilePath& path);
   // Sets the state to one of PROCESSING, WILL_RETRY or ERROR.
   void SetDistilledState(DistillationState distilled_state);
   // Sets the read state of the entry. Will set the UpdateTime of the entry.
   void SetRead(bool read);
 
@@ skipping 20 matching lines @@
   // These value are in microseconds since Jan 1st 1970. They are used for
   // sorting the entries from the database. They are kept in int64_t to avoid
   // conversion on each save/read event.
   int64_t creation_time_us_;
   int64_t update_time_us_;
 
   DISALLOW_COPY_AND_ASSIGN(ReadingListEntry);
 };
 
 #endif  // COMPONENTS_READING_LIST_IOS_READING_LIST_ENTRY_H_