Use a vector of smart pointers for callback return type.

components/offline_pages/background/request_queue_store.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_OFFLINE_PAGES_BACKGROUND_REQUEST_QUEUE_STORE_H_
 #define COMPONENTS_OFFLINE_PAGES_BACKGROUND_REQUEST_QUEUE_STORE_H_
 
 #include <stdint.h>
 #include <vector>
 
 #include "base/callback.h"
 #include "components/offline_pages/background/request_queue.h"
 #include "components/offline_pages/background/save_page_request.h"
 #include "components/offline_pages/offline_page_item.h"
 
 namespace offline_pages {
 
 // Interface for classes storing save page requests.
 class RequestQueueStore {
  public:
   enum class UpdateStatus {
     ADDED,    // Request was added successfully.
     UPDATED,  // Request was updated successfully.
     FAILED,   // Add or update attempt failed.
   };
 
   typedef base::Callback<void(
       bool /* success */,
-      const std::vector<SavePageRequest>& /* requests */)>
+      std::vector<std::unique_ptr<SavePageRequest>> /* requests */)>
       GetRequestsCallback;
   typedef base::Callback<void(UpdateStatus)> UpdateCallback;
   typedef base::Callback<void(
       const RequestQueue::UpdateMultipleRequestResults& /* statuses*/,
-      const std::vector<SavePageRequest>& /* requests */)>
+      std::vector<std::unique_ptr<SavePageRequest>> /* requests */)>
       UpdateMultipleRequestsCallback;
   typedef base::Callback<void(
       const RequestQueue::UpdateMultipleRequestResults& /* statuses */,
-      const std::vector<SavePageRequest>& /* requests */)>
+      std::vector<std::unique_ptr<SavePageRequest>> /* requests */)>
       RemoveCallback;
   typedef base::Callback<void(bool /* success */)> ResetCallback;
 
   virtual ~RequestQueueStore(){};
 
   // Gets all of the requests from the store.
   virtual void GetRequests(const GetRequestsCallback& callback) = 0;
 
   // Asynchronously adds or updates request in store.
   // Result of the update is passed in the callback.
@@ skipping 15 matching lines @@
       const SavePageRequest::RequestState new_state,
       const UpdateMultipleRequestsCallback& callback) = 0;
 
   // Resets the store.
   virtual void Reset(const ResetCallback& callback) = 0;
 };
 
 }  // namespace offline_pages
 
 #endif  // COMPONENTS_OFFLINE_PAGES_BACKGROUND_REQUEST_QUEUE_STORE_H_