[Doodle] Automatically expire Doodles after their TTL

components/doodle/doodle_service.h

 // Copyright 2017 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_DOODLE_DOODLE_SERVICE_H_
 #define COMPONENTS_DOODLE_DOODLE_SERVICE_H_
 
 #include <memory>
 
 #include "base/macros.h"
 #include "base/observer_list.h"
 #include "base/optional.h"
+#include "base/timer/timer.h"
 #include "components/doodle/doodle_fetcher.h"
 #include "components/doodle/doodle_types.h"
 
 namespace base {
 class TimeDelta;
 }
 
 namespace doodle {
 
 class DoodleService {
  public:
   class Observer {
    public:
     virtual void OnDoodleConfigUpdated(const base::Optional<DoodleConfig>&) = 0;
   };
 
-  DoodleService(std::unique_ptr<DoodleFetcher> fetcher);
+  // Both |fetcher| and |expiry_timer| must be non-null.
+  DoodleService(std::unique_ptr<DoodleFetcher> fetcher,
+                std::unique_ptr<base::OneShotTimer> expiry_timer);
   ~DoodleService();
 
   // Returns the current (cached) config, if any.
   const base::Optional<DoodleConfig>& config() const { return cached_config_; }
 
   // Adds a new observer to the service. It'll only be called when the config
   // changes; to get the current (cached) config, call |config()|.
   void AddObserver(Observer* observer);
 
   // Prevents |observer| from receiving future updates. This is safe to call
   // even when the observer is being notified of an update.
   void RemoveObserver(Observer* observer);
 
   // Requests an asynchronous refresh of the DoodleConfig from the network.
   // After the update completes, the observers will be notified only if the
   // config changed.
   void Refresh();
 
  private:
+  // Callback for the fetcher.
   void DoodleFetched(DoodleState state,
                      base::TimeDelta time_to_live,
                      const base::Optional<DoodleConfig>& doodle_config);
 
+  void UpdateTimeToLive(base::TimeDelta time_to_live);
+
+  // Callback for the expiry timer.
+  void DoodleExpired();
+
   // The fetcher for getting fresh DoodleConfigs from the network.
   std::unique_ptr<DoodleFetcher> fetcher_;
 
+  std::unique_ptr<base::OneShotTimer> expiry_timer_;
+
   // The result of the last network fetch.
   base::Optional<DoodleConfig> cached_config_;
 
   // The list of observers to be notified when the DoodleConfig changes.
   base::ObserverList<Observer> observers_;
 
   DISALLOW_COPY_AND_ASSIGN(DoodleService);
 };
 
 }  // namespace doodle
 
 #endif  // COMPONENTS_DOODLE_DOODLE_SERVICE_H_