[NTP Snippets] Schedule periodic fetching

ios/chrome/browser/ntp_snippets/ios_chrome_ntp_snippets_service_factory.cc

Index: ios/chrome/browser/ntp_snippets/ios_chrome_ntp_snippets_service_factory.cc
diff --git a/ios/chrome/browser/ntp_snippets/ios_chrome_ntp_snippets_service_factory.cc b/ios/chrome/browser/ntp_snippets/ios_chrome_ntp_snippets_service_factory.cc
index ebecc8891fcee8c368ecbae811cf293b438472d5..fb6d4e42947300afc8350aad3711a322841772ff 100644
--- a/ios/chrome/browser/ntp_snippets/ios_chrome_ntp_snippets_service_factory.cc
+++ b/ios/chrome/browser/ntp_snippets/ios_chrome_ntp_snippets_service_factory.cc
@@ -54,13 +54,15 @@ IOSChromeNTPSnippetsServiceFactory::BuildServiceInstanceFor(
   scoped_refptr<net::URLRequestContextGetter> request_context =
       browser_state->GetRequestContext();
 
+  ntp_snippets::NTPSnippetsScheduler* scheduler = nullptr;
+
   scoped_refptr<base::SequencedTaskRunner> task_runner =
       web::WebThread::GetBlockingPool()
           ->GetSequencedTaskRunnerWithShutdownBehavior(
               base::SequencedWorkerPool::GetSequenceToken(),
               base::SequencedWorkerPool::CONTINUE_ON_SHUTDOWN);
   return new ntp_snippets::NTPSnippetsService(
-      task_runner, GetApplicationContext()->GetApplicationLocale(),
+      task_runner, GetApplicationContext()->GetApplicationLocale(), scheduler,
       make_scoped_ptr(new ntp_snippets::NTPSnippetsFetcher(
           task_runner, signin_manager, token_service, request_context.get(),
           BrowserState::GetStatePath())));