[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 e826d0a9f9ce4b4996f53f5c6e940f6150a85618..c7e043caaf3bbd73204499345cf65b166806f0fc 100644
--- a/components/offline_pages/core/prefetch/prefetch_dispatcher_impl.h
+++ b/components/offline_pages/core/prefetch/prefetch_dispatcher_impl.h
@@ -21,9 +21,14 @@ 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:
+  void DisposeTask();
+
+  std::unique_ptr<ScopedBackgroundTask> task_;
+
   DISALLOW_COPY_AND_ASSIGN(PrefetchDispatcherImpl);
 };