[NTP Snippets] Don't reschedule background fetching on every startup

components/ntp_snippets/ntp_snippets_service.h

Index: components/ntp_snippets/ntp_snippets_service.h
diff --git a/components/ntp_snippets/ntp_snippets_service.h b/components/ntp_snippets/ntp_snippets_service.h
index 86e375962bf7ccd5bd9c945308a83402019edcc7..bbe2c3ec6b0de25184a2af9ba52811b4943511ae 100644
--- a/components/ntp_snippets/ntp_snippets_service.h
+++ b/components/ntp_snippets/ntp_snippets_service.h
@@ -108,8 +108,10 @@ class NTPSnippetsService : public ContentSuggestionsProvider,
     return snippets_fetcher_.get();
   }
 
-  // (Re)schedules the periodic fetching of snippets.
-  void RescheduleFetching();
+  // (Re)schedules the periodic fetching of snippets. If |force| is true, the
+  // tasks will be re-scheduled even if they already exist and have the correct
+  // periods.
+  void RescheduleFetching(bool force);
 
   // ContentSuggestionsProvider implementation
   CategoryStatus GetCategoryStatus(Category category) override;