[NTP Snippets] More reliable service initialization

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 159 matching lines @@
     //             that case the service will stay disabled until it is shut
     //             down. It can also enter this state after the database is
     //             done loading and GetStateForDependenciesStatus identifies
     //             the next state to be DISABLED.
     // - READY: if GetStateForDependenciesStatus returns it, after the database
     //          is done loading.
     NOT_INITED,
 
     // The service registered observers, timers, etc. and is ready to answer to
     // queries, fetch snippets... Can change to states:
-    // - READY: noop
     // - DISABLED: when the global Chrome state changes, for example after
     //             |OnStateChanged| is called and sync is disabled.
     // - SHUT_DOWN: when |Shutdown| is called, during the browser shutdown.
     READY,
 
     // The service is disabled and unregistered the related resources.
     // Can change to states:
-    // - DISABLED: noop
     // - READY: when the global Chrome state changes, for example after
     //          |OnStateChanged| is called and sync is enabled.
     // - SHUT_DOWN: when |Shutdown| is called, during the browser shutdown.
     DISABLED,
 
     // The service shutdown and can't be used anymore. This state is checked
     // for early exit in callbacks from observers.
     SHUT_DOWN
   };
 
   // sync_driver::SyncServiceObserver implementation.
   void OnStateChanged() override;
 
   // Callback for the NTPSnippetsDatabase.
   void OnDatabaseLoaded(NTPSnippet::PtrVector snippets);
 
   // 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);
 
   std::set<std::string> GetSnippetHostsFromPrefs() const;
   void StoreSnippetHostsToPrefs(const std::set<std::string>& hosts);
 
+  // Removes the expired snippets (including discarded) from the service and the
+  // database, and schedules another pass for the next expiration.
+  void ClearExpiredSnippets();
+
+  // Completes the initialization phase of the service, registering the last
+  // observers. This is done after construction, once the database is loaded.
+  void FinishInitialization();
+
   void LoadingSnippetsFinished();
 
   // Returns whether the service should be enabled or disable depending on its
   // internal state and the state of its dependencies.
   State GetStateForDependenciesStatus();
 
   // Verifies state transitions (see |State|'s documentation) and applies them.
+  // Does nothing if called with the current state.
   void EnterState(State state);
 
   // Enables the service and triggers a fetch if required. Do not call directly,
   // use |EnterState| instead.
   void EnterStateEnabled(bool fetch_snippets);
 
   // Disables the service. Do not call directly, use |EnterState| instead.
   void EnterStateDisabled();
 
   // Applies the effects of the transition to the SHUT_DOWN state. Do not call
@@ skipping 72 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_