Use a vector of smart pointers for callback return type.

components/offline_pages/background/request_picker.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_PICKER_H_
 #define COMPONENTS_OFFLINE_PAGES_BACKGROUND_REQUEST_PICKER_H_
 
 #include <memory>
 
 #include "base/memory/weak_ptr.h"
@@ skipping 19 matching lines @@
 
   // Choose which request we should process next based on the current
   // conditions, and call back to the RequestCoordinator when we have one.
   void ChooseNextRequest(
       RequestCoordinator::RequestPickedCallback picked_callback,
       RequestCoordinator::RequestNotPickedCallback not_picked_callback,
       DeviceConditions* device_conditions);
 
  private:
   // Callback for the GetRequest results to be delivered.
-  void GetRequestResultCallback(RequestQueue::GetRequestsResult result,
-                                const std::vector<SavePageRequest>& results);
+  void GetRequestResultCallback(
+      RequestQueue::GetRequestsResult result,
+      std::vector<std::unique_ptr<SavePageRequest>> results);
 
   // Filter out requests that don't meet the current conditions.  For instance,
   // if this is a predictive request, and we are not on WiFi, it should be
   // ignored this round.
-  bool RequestConditionsSatisfied(const SavePageRequest& request);
+  bool RequestConditionsSatisfied(const SavePageRequest* request);
 
   // Using policies, decide if the new request is preferable to the best we have
   // so far.
   bool IsNewRequestBetter(const SavePageRequest* oldRequest,
                           const SavePageRequest* newRequest,
                           RequestCompareFunction comparator);
 
   // Is the new request preferable from the retry count first standpoint?
   bool RetryCountFirstCompareFunction(const SavePageRequest* left,
                                       const SavePageRequest* right);
 
   // Is the new request better from the recency first standpoint?
   bool RecencyFirstCompareFunction(const SavePageRequest* left,
                                    const SavePageRequest* right);
 
   // Does the new request have better retry count?
   int CompareRetryCount(const SavePageRequest* left,
                         const SavePageRequest* right);
 
   // Does the new request have better creation time?
   int CompareCreationTime(const SavePageRequest* left,
                           const SavePageRequest* right);
 
-  // Split all requests into expired ones and still valid ones.
-  void SplitRequests(const std::vector<SavePageRequest>& requests,
-                     std::vector<SavePageRequest>& valid_requests,
-                     std::vector<SavePageRequest>& expired_requests);
+  // Split all requests into expired ones and still valid ones.  Takes ownership
+  // of the requests, and moves them into either valid or expired requests.
+  void SplitRequests(
+      std::vector<std::unique_ptr<SavePageRequest>> requests,
+      std::vector<std::unique_ptr<SavePageRequest>>* valid_requests,
+      std::vector<std::unique_ptr<SavePageRequest>>* expired_requests);
 
   // Callback used after requests get expired.
   void OnRequestExpired(
       const RequestQueue::UpdateMultipleRequestResults& results,
-      const std::vector<SavePageRequest>& requests);
+      const std::vector<std::unique_ptr<SavePageRequest>> requests);
 
   // Unowned pointer to the request queue.
   RequestQueue* queue_;
   // Unowned pointer to the policy object.
   OfflinerPolicy* policy_;
   // Unowned pointer to the request coordinator.
   RequestNotifier* notifier_;
   // Current conditions on the device
   std::unique_ptr<DeviceConditions> current_conditions_;
   // True if we prefer less-tried requests
   bool fewer_retries_better_;
   // True if we prefer requests submitted more recently
   bool earlier_requests_better_;
   // Callback for when we are done picking a request to do next.
   RequestCoordinator::RequestPickedCallback picked_callback_;
   // Callback for when there are no more reqeusts to pick.
   RequestCoordinator::RequestNotPickedCallback not_picked_callback_;
   // Allows us to pass a weak pointer to callbacks.
   base::WeakPtrFactory<RequestPicker> weak_ptr_factory_;
 };
 
 }  // namespace offline_pages
 
 #endif  // COMPONENTS_OFFLINE_PAGES_BACKGROUND_REQUEST_PICKER_H_