Use a vector of smart pointers for callback return type.

components/offline_pages/background/request_queue_in_memory_store.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/offline_pages/background/request_queue_in_memory_store.h"
 
 #include "base/bind.h"
 #include "base/location.h"
 #include "base/threading/thread_task_runner_handle.h"
 #include "components/offline_pages/background/save_page_request.h"
 
 namespace offline_pages {
 
 RequestQueueInMemoryStore::RequestQueueInMemoryStore() {}
 
 RequestQueueInMemoryStore::~RequestQueueInMemoryStore() {}
 
 void RequestQueueInMemoryStore::GetRequests(
     const GetRequestsCallback& callback) {
-  std::vector<SavePageRequest> result_requests;
-  for (const auto& id_request_pair : requests_)
-    result_requests.push_back(id_request_pair.second);
+  std::vector<std::unique_ptr<SavePageRequest>> result_requests;
+  for (const auto& id_request_pair : requests_) {
+    std::unique_ptr<SavePageRequest> request(
+        new SavePageRequest(id_request_pair.second));
+    result_requests.push_back(std::move(request));
+  }
   base::ThreadTaskRunnerHandle::Get()->PostTask(
-      FROM_HERE, base::Bind(callback, true, result_requests));
+      FROM_HERE,
+      base::Bind(callback, true, base::Passed(std::move(result_requests))));
 }
 
 void RequestQueueInMemoryStore::AddOrUpdateRequest(
     const SavePageRequest& request,
     const UpdateCallback& callback) {
   RequestsMap::iterator iter = requests_.find(request.request_id());
   if (iter != requests_.end())
     requests_.erase(iter);
   requests_.insert(std::make_pair(request.request_id(), request));
   base::ThreadTaskRunnerHandle::Get()->PostTask(
       FROM_HERE, base::Bind(callback, UpdateStatus::UPDATED));
 }
 
 void RequestQueueInMemoryStore::RemoveRequests(
     const std::vector<int64_t>& request_ids,
     const RemoveCallback& callback) {
   RequestQueue::UpdateMultipleRequestResults results;
   RequestQueue::UpdateRequestResult result;
-  std::vector<SavePageRequest> requests;
+  std::vector<std::unique_ptr<SavePageRequest>> requests;
   RequestsMap::iterator iter;
 
   // If we find a request, mark it as succeeded, and put it in the request list.
   // Otherwise mark it as failed.
   for (auto request_id : request_ids) {
     iter = requests_.find(request_id);
     if (iter != requests_.end()) {
-      SavePageRequest request = iter->second;
+      std::unique_ptr<SavePageRequest> request(
+          new SavePageRequest(iter->second));
       requests_.erase(iter);
       result = RequestQueue::UpdateRequestResult::SUCCESS;
-      requests.push_back(request);
+      requests.push_back(std::move(request));
     } else {
       result = RequestQueue::UpdateRequestResult::REQUEST_DOES_NOT_EXIST;
     }
     results.push_back(std::make_pair(request_id, result));
   }
 
   base::ThreadTaskRunnerHandle::Get()->PostTask(
-      FROM_HERE, base::Bind(callback, results, requests));
+      FROM_HERE,
+      base::Bind(callback, results, base::Passed(std::move(requests))));
 }
 
 void RequestQueueInMemoryStore::ChangeRequestsState(
     const std::vector<int64_t>& request_ids,
     const SavePageRequest::RequestState new_state,
     const UpdateMultipleRequestsCallback& callback) {
   RequestQueue::UpdateMultipleRequestResults results;
-  std::vector<SavePageRequest> requests;
+  std::vector<std::unique_ptr<SavePageRequest>> requests;
   RequestQueue::UpdateRequestResult result;
   for (int64_t request_id : request_ids) {
     auto pair = requests_.find(request_id);
     // If we find this request id, modify it, and return the modified request in
     // the request list.
     if (pair != requests_.end()) {
       pair->second.set_request_state(new_state);
-      requests.push_back(pair->second);
+      std::unique_ptr<SavePageRequest> request(
+          new SavePageRequest(pair->second));
+      requests.push_back(std::move(request));
       result = RequestQueue::UpdateRequestResult::SUCCESS;
     } else {
       result = RequestQueue::UpdateRequestResult::REQUEST_DOES_NOT_EXIST;;
     }
 
     results.push_back(std::make_pair(request_id, result));
   }
 
   base::ThreadTaskRunnerHandle::Get()->PostTask(
-      FROM_HERE, base::Bind(callback, results, requests));
+      FROM_HERE,
+      base::Bind(callback, results, base::Passed(std::move(requests))));
 }
 
 void RequestQueueInMemoryStore::Reset(const ResetCallback& callback) {
   requests_.clear();
   base::ThreadTaskRunnerHandle::Get()->PostTask(FROM_HERE,
                                                 base::Bind(callback, true));
 }
 
 }  // namespace offline_pages