[NTP Snippets] Shut down the service on database failure

components/ntp_snippets/ntp_snippets_service.h

 // Copyright 2015 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #ifndef COMPONENTS_NTP_SNIPPETS_NTP_SNIPPETS_SERVICE_H_
 #define COMPONENTS_NTP_SNIPPETS_NTP_SNIPPETS_SERVICE_H_
 
 #include <stddef.h>
 
 #include <memory>
@@ skipping 188 matching lines @@
     SHUT_DOWN
   };
 
   // sync_driver::SyncServiceObserver implementation.
   void OnStateChanged() override;
 
   // image_fetcher::ImageFetcherDelegate implementation.
   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);
 
   // Callback for the NTPSnippetsFetcher.
   void OnFetchFinished(NTPSnippetsFetcher::OptionalSnippets snippets);
 
   // Merges newly available snippets with the previously available list.
   void MergeSnippets(NTPSnippet::PtrVector new_snippets);
 
@@ skipping 113 matching lines @@
   // or because a requirement (e.g. History Sync) is not fulfilled anymore.
   virtual void NTPSnippetsServiceDisabled() = 0;
 
  protected:
   virtual ~NTPSnippetsServiceObserver() {}
 };
 
 }  // namespace ntp_snippets
 
 #endif  // COMPONENTS_NTP_SNIPPETS_NTP_SNIPPETS_SERVICE_H_