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

components/offline_pages/content/suggested_articles_observer_unittest.cc

Index: components/offline_pages/content/suggested_articles_observer_unittest.cc
diff --git a/components/offline_pages/content/suggested_articles_observer_unittest.cc b/components/offline_pages/content/suggested_articles_observer_unittest.cc
index 9d262b0dca425af33903d34676e5ae707c92454d..2a988ddf3673abb16806b75846de6321a0650e82 100644
--- a/components/offline_pages/content/suggested_articles_observer_unittest.cc
+++ b/components/offline_pages/content/suggested_articles_observer_unittest.cc
@@ -49,6 +49,10 @@ class TestingPrefetchService : public PrefetchService {
     last_removed_client_id = base::MakeUnique<ClientId>(client_id);
   }
 
+  void BeginBackgroundTask(
+      std::unique_ptr<ScopedBackgroundTask> task) override {}
+  void StopBackgroundTask(ScopedBackgroundTask* task) override {}
+
   std::vector<PrefetchURL> latest_prefetch_urls;
   std::unique_ptr<ClientId> last_removed_client_id;