[Offline Prefetch] Backoff support for PrefetchBackgroundTask

components/offline_pages/core/prefetch/prefetch_dispatcher_impl.h

Index: components/offline_pages/core/prefetch/prefetch_dispatcher_impl.h
diff --git a/components/offline_pages/core/prefetch/prefetch_dispatcher_impl.h b/components/offline_pages/core/prefetch/prefetch_dispatcher_impl.h
index 3764a5ba0bb991c0228ab3702bc9b428a3501834..d303dcf910548d6d37f797f7a31e6a96a05a62b8 100644
--- a/components/offline_pages/core/prefetch/prefetch_dispatcher_impl.h
+++ b/components/offline_pages/core/prefetch/prefetch_dispatcher_impl.h
@@ -26,13 +26,17 @@ class PrefetchDispatcherImpl : public PrefetchDispatcher {
   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;
+  void StopBackgroundTask() override;
+  void RequestFinishBackgroundTaskForTest() override;
 
  private:
   friend class PrefetchDispatcherTest;
 
+  void DisposeTask();
+
   PrefetchService* service_;
   TaskQueue task_queue_;
+  std::unique_ptr<ScopedBackgroundTask> task_;
 
   DISALLOW_COPY_AND_ASSIGN(PrefetchDispatcherImpl);
 };