[NTP Snippets] Implement snippets expiry

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 <string>
 #include <vector>
 
 #include "base/macros.h"
 #include "base/memory/weak_ptr.h"
 #include "base/observer_list.h"
 #include "base/sequenced_task_runner.h"
+#include "base/timer/timer.h"
 #include "components/keyed_service/core/keyed_service.h"
 #include "components/ntp_snippets/inner_iterator.h"
 #include "components/ntp_snippets/ntp_snippet.h"
 #include "components/ntp_snippets/ntp_snippets_fetcher.h"
 #include "components/ntp_snippets/ntp_snippets_scheduler.h"
 
 class PrefService;
 
 namespace base {
 class FilePath;
@@ skipping 76 matching lines @@
 
   // Expects a list of dictionaries each containing a "contentInfo" dictionary
   // with keys matching the properties of a  snippet (url, title, site_title,
   // etc...). The url is the only mandatory value.
   bool LoadFromJSONList(const base::ListValue& list);
 
   // TODO(treib): Investigate a better storage, maybe LevelDB or SQLite?
   void LoadFromPrefs();
   void StoreToPrefs();
 
+  void ScheduleExpiryTimer();
+
+  void RemoveExpiredSnippets();
+
   PrefService* pref_service_;
 
   // True if the suggestions are loaded.
   bool loaded_;
 
   // The SequencedTaskRunner on which file system operations will be run.
   scoped_refptr<base::SequencedTaskRunner> file_task_runner_;
 
   // All the suggestions.
   NTPSnippetStorage snippets_;
 
   // The ISO 639-1 code of the language used by the application.
   const std::string application_language_code_;
 
   // The observers.
   base::ObserverList<NTPSnippetsServiceObserver> observers_;
 
   // Scheduler for fetching snippets. Not owned.
   NTPSnippetsScheduler* scheduler_;
 
-  // The snippets fetcher
+  // The snippets fetcher.
   scoped_ptr<NTPSnippetsFetcher> snippets_fetcher_;
 
-  // The callback from the snippets fetcher
+  // The subscription to the snippets fetcher.
   scoped_ptr<NTPSnippetsFetcher::SnippetsAvailableCallbackList::Subscription>
       snippets_fetcher_callback_;
 
+  // Timer that calls us back when the next snippet expires.
+  base::OneShotTimer expiry_timer_;
+
   base::WeakPtrFactory<NTPSnippetsService> weak_ptr_factory_;
 
   friend class NTPSnippetsServiceTest;
   FRIEND_TEST_ALL_PREFIXES(NTPSnippetsServiceTest, Loop);
   FRIEND_TEST_ALL_PREFIXES(NTPSnippetsServiceTest, Full);
   FRIEND_TEST_ALL_PREFIXES(NTPSnippetsServiceTest, ObserverLoaded);
   FRIEND_TEST_ALL_PREFIXES(NTPSnippetsServiceTest, ObserverNotLoaded);
 
   DISALLOW_COPY_AND_ASSIGN(NTPSnippetsService);
 };
 
 class NTPSnippetsServiceObserver {
  public:
   // Send everytime the service loads a new set of data.
   virtual void NTPSnippetsServiceLoaded(NTPSnippetsService* service) = 0;
   // Send when the service is shutting down.
   virtual void NTPSnippetsServiceShutdown(NTPSnippetsService* service) = 0;
 
  protected:
   virtual ~NTPSnippetsServiceObserver() {}
 };
 
 }  // namespace ntp_snippets
 
 #endif  // COMPONENTS_NTP_SNIPPETS_NTP_SNIPPETS_SERVICE_H_