[NTP Snippets] Unschedule fetches when the service should be disabled

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 31 matching lines @@
 namespace suggestions {
 class SuggestionsProfile;
 }
 
 namespace sync_driver {
 class SyncService;
 }
 
 namespace ntp_snippets {
 
+enum class DisabledReason {
+  // Snippets are enabled
+  NONE,
+  // Snippets have been disabled as part of the service configuration.
+  EXPLICITLY_DISABLED,
+  // History sync is not enabled, and the service requires it to be enabled.
+  HISTORY_SYNC_DISABLED
+};
+
 class NTPSnippetsDatabase;
 class NTPSnippetsServiceObserver;
 
 // Stores and vends fresh content data for the NTP.
 class NTPSnippetsService : public KeyedService,
                            public sync_driver::SyncServiceObserver {
  public:
   using ImageFetchedCallback =
       base::Callback<void(const std::string& snippet_id, const gfx::Image&)>;
 
@@ skipping 62 matching lines @@
   // Clears the lists of snippets previously discarded by the user.
   void ClearDiscardedSnippets();
 
   // Returns the lists of suggestion hosts the snippets are restricted to.
   std::set<std::string> GetSuggestionsHosts() const;
 
   // Observer accessors.
   void AddObserver(NTPSnippetsServiceObserver* observer);
   void RemoveObserver(NTPSnippetsServiceObserver* observer);
 
+  // Returns a reason why the service could be disabled, or DisabledReason::NONE
+  // if it's not.
+  DisabledReason GetDisabledReason();
+
   // Returns the maximum number of snippets that will be shown at once.
   static int GetMaxSnippetCountForTesting();
 
  private:
   FRIEND_TEST_ALL_PREFIXES(NTPSnippetsServiceWithSyncTest,
                            SyncStateCompatibility);
   FRIEND_TEST_ALL_PREFIXES(NTPSnippetsServiceWithSyncTest,
                            HistorySyncStateChanges);
 
+  // Possible state transitions:
+  //           NOT_INITED ---------------+
+  //               v                     |
+  //  +--------- INITED   <------+       |
+  //  |            v             |       |
+  //  |     LOADED = READY -> DISABLED <-+
+  //  |            v             |
+  //  +------> SHUT_DOWN  <------+
+  enum class State {
+    NOT_INITED,
+    INITED,
+    LOADED,
+    READY = LOADED,

[Marc Treib, 2016/05/24 09:04:46]

Why READY and LOADED? Can we stick with just one? (READY is probably a better
name than LOADED)

[dgn, 2016/05/24 18:13:30]

That was in case we have more intermediate states, to have the reference to the
READY state be able to easily move. Removed that.

+    DISABLED,
+    SHUT_DOWN
+  };
+
   // sync_driver::SyncServiceObserver implementation.
   void OnStateChanged() override;
 
   // Callback for the NTPSnippetsDatabase.
   void OnSnippetsLoaded(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);
 
   void LoadingSnippetsFinished();
 
-  // Checks whether the state of the sync service is incompatible with showing
-  // snippets. We need history sync to be active.
-  // Note: The state is considered compatible if the service is still
-  // initializing and the sync state is not known.
-  bool IsSyncStateIncompatible();
+  // Enable the service. Do not call directly, use |EnterState| instead.
+  void Enable();
 
-  enum class State {
-    NOT_INITED,
-    INITED,
-    LOADED,
-    SHUT_DOWN
-  } state_;
+  // Disable the service. Do not call directly, use |EnterState| instead.
+  void Disable();
 
-  bool enabled_;
+  // Applies state transitions (see |State|'s documentation )and verifies them.
+  void EnterState(State state);
+
+  State state_;
+
+  // The service was set up to be disabled and should not be enabled by any
+  // state change. We track this to make sure we clear scheduled tasks, which
+  // persist even when Chrome is stopped.
+  bool explicitly_disabled_;
 
   PrefService* pref_service_;
 
   sync_driver::SyncService* sync_service_;
 
   // The observer for the SyncService. When the sync state changes,
   // SyncService will call |OnStateChanged|, which is propagated to the
   // snippet observers.
   ScopedObserver<sync_driver::SyncService, sync_driver::SyncServiceObserver>
       sync_service_observer_;
@@ skipping 47 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_