[NTP Snippets] Shut down the service on database failure

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 1b1295c916572535b28a392b16255318f95e910a..57542c118dacd18af251ddc534d2f28aab0503fd 100644
--- a/components/ntp_snippets/ntp_snippets_service.h
+++ b/components/ntp_snippets/ntp_snippets_service.h
@@ -206,8 +206,9 @@ class NTPSnippetsService : public KeyedService,
   void OnImageDataFetched(const std::string& snippet_id,
                           const std::string& image_data) override;
 
-  // Callback for the NTPSnippetsDatabase.
+  // Callbacks for the NTPSnippetsDatabase.
   void OnDatabaseLoaded(NTPSnippet::PtrVector snippets);
+  void OnDatabaseError();
 
   // Callback for the SuggestionsService.
   void OnSuggestionsChanged(const suggestions::SuggestionsProfile& suggestions);