Make reading list entry movable only

ios/chrome/browser/reading_list/reading_list_entry.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 "ios/chrome/browser/reading_list/reading_list_entry.h"
 
 ReadingListEntry::ReadingListEntry(const GURL& url, const std::string& title)
     : url_(url), title_(title), distilled_state_(WAITING) {
   DCHECK(!url.is_empty());
   DCHECK(url.is_valid());
 }
-ReadingListEntry::ReadingListEntry(const ReadingListEntry& entry)
+ReadingListEntry::ReadingListEntry(ReadingListEntry&& entry)
     : url_(entry.URL()),
       title_(entry.Title()),
       distilled_url_(entry.DistilledURL()),
       distilled_state_(entry.DistilledState()) {}
 ReadingListEntry::~ReadingListEntry() {}
 
 const GURL& ReadingListEntry::URL() const {
   return url_;
 }
 
 const std::string ReadingListEntry::Title() const {
   return title_;
 }
 
 ReadingListEntry::DistillationState ReadingListEntry::DistilledState() const {
   return distilled_state_;
 }
 
 const GURL& ReadingListEntry::DistilledURL() const {
   return distilled_url_;
 }
 
-ReadingListEntry& ReadingListEntry::operator=(const ReadingListEntry& other) {
+ReadingListEntry& ReadingListEntry::operator=(ReadingListEntry&& other) {
   url_ = other.url_;
   title_ = other.title_;
   distilled_url_ = other.distilled_url_;
   distilled_state_ = other.distilled_state_;
   return *this;
 }
 
 bool ReadingListEntry::operator==(const ReadingListEntry& other) const {
   return url_ == other.url_;
 }
 
 void ReadingListEntry::SetTitle(const std::string& title) {
   title_ = title;
 }
 
 void ReadingListEntry::SetDistilledURL(const GURL& url) {
   DCHECK(url.is_valid());
   distilled_url_ = url;
   distilled_state_ = PROCESSED;
 }
 
 void ReadingListEntry::SetDistilledState(DistillationState distilled_state) {
   DCHECK(distilled_state != PROCESSED);  // use SetDistilledURL instead.
   DCHECK(distilled_state != WAITING);
   distilled_state_ = distilled_state;
   distilled_url_ = GURL();
 }