[Offline Prefetch] Create a new JobScheduler task to wake up for net activity.

components/offline_pages/core/prefetch/prefetch_service_impl.h

 // Copyright 2017 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_CORE_PREFETCH_PREFETCH_SERVICE_IMPL_H_
 #define COMPONENTS_OFFLINE_PAGES_CORE_PREFETCH_PREFETCH_SERVICE_IMPL_H_
 
 #include <vector>
 
 #include "components/offline_pages/core/prefetch/prefetch_service.h"
 #include "url/gurl.h"
 
 namespace offline_pages {
 
 class PrefetchServiceImpl : public PrefetchService {
  public:
   PrefetchServiceImpl();
   ~PrefetchServiceImpl() override;
 
   // PrefetchService implementation:
   void AddCandidatePrefetchURLs(
       const std::vector<PrefetchURL>& suggested_urls) override;
   void RemoveAllUnprocessedPrefetchURLs(const std::string& name_space) override;
   void RemovePrefetchURLsByClientId(const ClientId& client_id) override;
+  void BeginBackgroundTask(std::unique_ptr<ScopedBackgroundTask> task) override;
+  void StopBackgroundTask(ScopedBackgroundTask* task) override;
 
   // KeyedService implementation:
   void Shutdown() override;
 
  private:
   DISALLOW_COPY_AND_ASSIGN(PrefetchServiceImpl);
 };
 
 }  // namespace offline_pages
 
 #endif  // COMPONENTS_OFFLINE_PAGES_CORE_PREFETCH_PREFETCH_SERVICE_IMPL_H_