Use a vector of smart pointers for callback return type.

components/offline_pages/background/request_coordinator.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_COORDINATOR_H_
 #define COMPONENTS_OFFLINE_PAGES_BACKGROUND_REQUEST_COORDINATOR_H_
 
 #include <memory>
 
 #include "base/callback.h"
@@ skipping 71 matching lines @@
   void RemoveRequests(const std::vector<int64_t>& request_ids,
                       const RemoveRequestsCallback& callback);
 
   // Pause a list of requests by |request_id|.  This will change the state
   // in the request queue so the request cannot be started.
   void PauseRequests(const std::vector<int64_t>& request_ids);
 
   // Resume a list of previously paused requests, making them available.
   void ResumeRequests(const std::vector<int64_t>& request_ids);
 
-  // Callback that receives the response for GetAllRequests.  Client must
-  // copy the result right away, it goes out of scope at the end of the
-  // callback.
-  typedef base::Callback<void(const std::vector<SavePageRequest>&)>
+  // Callback that receives the response for GetAllRequests.
+  typedef base::Callback<void(std::vector<std::unique_ptr<SavePageRequest>>)>
       GetRequestsCallback;
 
   // Get all save page request items in the callback.
   void GetAllRequests(const GetRequestsCallback& callback);
 
   // Starts processing of one or more queued save page later requests.
   // Returns whether processing was started and that caller should expect
   // a callback. If processing was already active, returns false.
   bool StartProcessing(const DeviceConditions& device_conditions,
                        const base::Callback<void(bool)>& callback);
@@ skipping 54 matching lines @@
     return is_stopped_;
   }
 
   OfflineEventLogger* GetLogger() {
     return &event_logger_;
   }
 
  private:
   // Receives the results of a get from the request queue, and turns that into
   // SavePageRequest objects for the caller of GetQueuedRequests.
-  void GetQueuedRequestsCallback(const GetRequestsCallback& callback,
-                                 RequestQueue::GetRequestsResult result,
-                                 const std::vector<SavePageRequest>& requests);
+  void GetQueuedRequestsCallback(
+      const GetRequestsCallback& callback,
+      RequestQueue::GetRequestsResult result,
+      std::vector<std::unique_ptr<SavePageRequest>> requests);
 
   // Receives the results of a get from the request queue, and turns that into
   // SavePageRequest objects for the caller of GetQueuedRequests.
   void GetRequestsForSchedulingCallback(
       RequestQueue::GetRequestsResult result,
-      const std::vector<SavePageRequest>& requests);
+      std::vector<std::unique_ptr<SavePageRequest>> requests);
 
   // Receives the result of add requests to the request queue.
   void AddRequestResultCallback(RequestQueue::AddRequestResult result,
                                 const SavePageRequest& request);
 
   // Receives the result of update and delete requests to the request queue.
   void UpdateRequestCallback(const ClientId& client_id,
                              RequestQueue::UpdateRequestResult result);
 
   void UpdateMultipleRequestsCallback(
       const RequestQueue::UpdateMultipleRequestResults& result,
-      const std::vector<SavePageRequest>& requests);
+      std::vector<std::unique_ptr<SavePageRequest>> requests);
 
   void HandleRemovedRequestsAndCallback(
       const RemoveRequestsCallback& callback,
       BackgroundSavePageResult status,
       const RequestQueue::UpdateMultipleRequestResults& results,
-      const std::vector<SavePageRequest>& requests);
+      std::vector<std::unique_ptr<SavePageRequest>> requests);
 
   void HandleRemovedRequests(
       BackgroundSavePageResult status,
       const RequestQueue::UpdateMultipleRequestResults& results,
-      const std::vector<SavePageRequest>& requests);
+      std::vector<std::unique_ptr<SavePageRequest>> requests);
 
   // Start processing now if connected (but with conservative assumption
   // as to other device conditions).
   void StartProcessingIfConnected();
 
   // Check the request queue, and schedule a task corresponding
   // to the least restrictive type of request in the queue.
   void ScheduleAsNeeded();
 
   // Callback from the request picker when it has chosen our next request.
@@ skipping 96 matching lines @@
   base::TimeDelta offliner_timeout_;
   // Allows us to pass a weak pointer to callbacks.
   base::WeakPtrFactory<RequestCoordinator> weak_ptr_factory_;
 
   DISALLOW_COPY_AND_ASSIGN(RequestCoordinator);
 };
 
 }  // namespace offline_pages
 
 #endif  // COMPONENTS_OFFLINE_PAGES_BACKGROUND_REQUEST_COORDINATOR_H_