Split the RequestPicker task into two separate tasks.

components/offline_pages/background/cleanup_task.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_CLEANUP_TASK_H_
+#define COMPONENTS_OFFLINE_PAGES_BACKGROUND_CLEANUP_TASK_H_
+
+#include <set>
+
+#include "base/memory/weak_ptr.h"
+#include "components/offline_pages/background/request_queue_results.h"
+#include "components/offline_pages/background/save_page_request.h"
+#include "components/offline_pages/core/task.h"
+
+namespace offline_pages {
+
+class OfflinerPolicy;
+class RequestCoordinatorEventLogger;
+class RequestNotifier;
+class RequestQueueStore;
+
+class CleanupTask : public Task {
+ public:
+  CleanupTask(RequestQueueStore* store,
+              OfflinerPolicy* policy,
+              RequestNotifier* notifier,
+              RequestCoordinatorEventLogger* logger);
+  ~CleanupTask() override;
+
+  // TaskQueue::Task implementation, starts the async chain
+  void Run() override;
+
+ private:
+  // Step 1. get results from the store
+  void GetRequests();
+
+  // Step 2. Prune stale requests
+  void Prune(bool success,
+             std::vector<std::unique_ptr<SavePageRequest>> requests);
+
+  // Step 3. Handle deleting stale entries and notifying observers.
+  void RemoveStaleRequests(std::vector<int64_t> stale_request_ids);
+
+  // Step 4. Send delete notifications for the expired requests.
+  void OnRequestsExpired(std::unique_ptr<UpdateRequestsResult> result);
+
+  // Build a list of IDs whose request has expired.
+  void GetExpiredRequestIds(
+      std::vector<std::unique_ptr<SavePageRequest>> requests,
+      std::vector<int64_t>* expired_request_ids);
+
+  // Member variables, all pointers are not owned here.
+  RequestQueueStore* store_;
+  OfflinerPolicy* policy_;
+  RequestNotifier* notifier_;
+  RequestCoordinatorEventLogger* event_logger_;
+  // Allows us to pass a weak pointer to callbacks.
+  base::WeakPtrFactory<CleanupTask> weak_ptr_factory_;
+};
+
+}  // namespace offline_pages
+
+#endif  // COMPONENTS_OFFLINE_PAGES_BACKGROUND_CLEANUP_TASK_H_