Make reading list entry movable only

ios/chrome/browser/reading_list/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 "ios/chrome/browser/reading_list/reading_list_model_impl.h"
 
 #include "ios/chrome/browser/reading_list/reading_list_model_storage.h"
 #include "url/gurl.h"
 
 ReadingListModelImpl::ReadingListModelImpl() : ReadingListModelImpl(NULL) {}
@@ skipping 85 matching lines @@
                       ReadingListDidApplyChanges(this));
     return;
   }
 }
 
 const ReadingListEntry& ReadingListModelImpl::AddEntry(
     const GURL& url,
     const std::string& title) {
   DCHECK(loaded());
   RemoveEntryByUrl(url);
-  const ReadingListEntry entry(url, title);
+  ReadingListEntry entry(url, title);
   FOR_EACH_OBSERVER(ReadingListModelObserver, observers_,
                     ReadingListWillAddUnreadEntry(this, entry));
-  unread_.insert(unread_.begin(), entry);
+  unread_.insert(unread_.begin(), std::move(entry));
   hasUnseen_ = true;
   if (storageLayer_ && !IsPerformingBatchUpdates()) {
     storageLayer_->SavePersistentUnreadList(unread_);
     storageLayer_->SavePersistentHasUnseen(true);
   }
   FOR_EACH_OBSERVER(ReadingListModelObserver, observers_,
                     ReadingListDidApplyChanges(this));
   return *unread_.begin();
 }
 
 void ReadingListModelImpl::MarkReadByURL(const GURL& url) {
   DCHECK(loaded());
-  const ReadingListEntry entry(url, std::string());
-
+  ReadingListEntry entry(url, std::string());
   auto result = std::find(unread_.begin(), unread_.end(), entry);
   if (result == unread_.end())
     return;
 
   FOR_EACH_OBSERVER(
       ReadingListModelObserver, observers_,
       ReadingListWillMoveEntry(this, std::distance(unread_.begin(), result)));
 
-  read_.insert(read_.begin(), *result);
+  read_.insert(read_.begin(), std::move(*result));
   unread_.erase(result);
+
   if (storageLayer_ && !IsPerformingBatchUpdates()) {
     storageLayer_->SavePersistentUnreadList(unread_);
     storageLayer_->SavePersistentReadList(read_);
   }
   FOR_EACH_OBSERVER(ReadingListModelObserver, observers_,
                     ReadingListDidApplyChanges(this));
 }
 
 void ReadingListModelImpl::SetEntryTitle(const GURL& url,
                                          const std::string& title) {
@@ skipping 94 matching lines @@
 
 void ReadingListModelImpl::EndBatchUpdates() {
   ReadingListModel::EndBatchUpdates();
   if (IsPerformingBatchUpdates() || !storageLayer_) {
     return;
   }
   storageLayer_->SavePersistentUnreadList(unread_);
   storageLayer_->SavePersistentReadList(read_);
   storageLayer_->SavePersistentHasUnseen(hasUnseen_);
 }