[Thumbnails DB] Add functionality to clear unused on-demand favicons.

components/history/core/browser/expire_history_backend.h

 // Copyright (c) 2012 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_HISTORY_CORE_BROWSER_EXPIRE_HISTORY_BACKEND_H_
 #define COMPONENTS_HISTORY_CORE_BROWSER_EXPIRE_HISTORY_BACKEND_H_
 
 #include <memory>
 #include <queue>
 #include <set>
 #include <vector>
 
 #include "base/gtest_prod_util.h"
 #include "base/macros.h"
 #include "base/memory/weak_ptr.h"
 #include "base/time/time.h"
 #include "components/history/core/browser/history_types.h"
 
 class GURL;
 class TestingProfile;
 
 namespace base {
+struct Feature;
 class SequencedTaskRunner;
 }
 
 namespace history {
 
 class HistoryBackendClient;
 class HistoryBackendNotifier;
 class HistoryDatabase;
 class ThumbnailDatabase;
 
 // Encapsulates visit expiration criteria and type of visits to expire.
 class ExpiringVisitsReader {
  public:
   virtual ~ExpiringVisitsReader() {}
   // Populates |visits| from |db|, using provided |end_time| and |max_visits|
   // cap.
   virtual bool Read(base::Time end_time, HistoryDatabase* db,
                     VisitVector* visits, int max_visits) const = 0;
 };
 
 typedef std::vector<const ExpiringVisitsReader*> ExpiringVisitsReaders;
 
+namespace internal {
+// Feature that enables clearing old on-demand favicons.
+extern const base::Feature kClearOldOnDemandFavicons;
+}  // namespace internal
+
 // Helper component to HistoryBackend that manages expiration and deleting of
 // history.
 //
 // It will automatically start periodically expiring old history once you call
 // StartExpiringOldStuff().
 class ExpireHistoryBackend {
  public:
   // The delegate pointer must be non-null. We will NOT take ownership of it.
   // HistoryBackendClient may be null. The HistoryBackendClient is used when
   // expiring URLS so that we don't remove any URLs or favicons that are
@@ skipping 40 matching lines @@
   // should not save it.
   base::Time GetCurrentExpirationTime() const {
     return base::Time::Now() - expiration_threshold_;
   }
 
  private:
   FRIEND_TEST_ALL_PREFIXES(ExpireHistoryTest, DeleteFaviconsIfPossible);
   FRIEND_TEST_ALL_PREFIXES(ExpireHistoryTest, ExpireSomeOldHistory);
   FRIEND_TEST_ALL_PREFIXES(ExpireHistoryTest, ExpiringVisitsReader);
   FRIEND_TEST_ALL_PREFIXES(ExpireHistoryTest, ExpireSomeOldHistoryWithSource);
+  FRIEND_TEST_ALL_PREFIXES(ExpireHistoryTest,
+                           ClearOldOnDemandFaviconsDoesNotDeleteStarred);
+  FRIEND_TEST_ALL_PREFIXES(ExpireHistoryTest,
+                           ClearOldOnDemandFaviconsDoesDeleteUnstarred);
+  FRIEND_TEST_ALL_PREFIXES(ExpireHistoryTest,
+                           ClearOldOnDemandFaviconsDoesDeleteAfterLongDelay);
+  FRIEND_TEST_ALL_PREFIXES(
+      ExpireHistoryTest,
+      ClearOldOnDemandFaviconsDoesNotDeleteAfterShortDelay);
+
   friend class ::TestingProfile;
 
   struct DeleteEffects {
     DeleteEffects();
     ~DeleteEffects();
 
     // The time range affected. These can be is_null() to be unbounded in one
     // or both directions.
     base::Time begin_time, end_time;
 
@@ skipping 84 matching lines @@
   void BroadcastNotifications(DeleteEffects* effects, DeletionType type);
 
   // Schedules a call to DoExpireIteration.
   void ScheduleExpire();
 
   // Calls ExpireSomeOldHistory to expire some amount of old history, according
   // to the items in work queue, and schedules another call to happen in the
   // future.
   void DoExpireIteration();
 
+  // Clears all old on-demand favicons from thumbnail database.
+  void ClearOldOnDemandFavicons(base::Time expiration_threshold);
+
   // Tries to expire the oldest |max_visits| visits from history that are older
   // than |time_threshold|. The return value indicates if we think there might
   // be more history to expire with the current time threshold (it does not
   // indicate success or failure).
   bool ExpireSomeOldHistory(base::Time end_time,
                              const ExpiringVisitsReader* reader,
                              int max_visits);
 
   // Tries to detect possible bad history or inconsistencies in the database
   // and deletes items. For example, URLs with no visits.
@@ skipping 14 matching lines @@
   // Non-owning pointer to the notification delegate (guaranteed non-NULL).
   HistoryBackendNotifier* notifier_;
 
   // Non-owning pointers to the databases we deal with (MAY BE NULL).
   HistoryDatabase* main_db_;       // Main history database.
   ThumbnailDatabase* thumb_db_;    // Thumbnails and favicons.
 
   // The threshold for "old" history where we will automatically delete it.
   base::TimeDelta expiration_threshold_;
 
+  // The lastly used threshold for "old" on-demand favicons.
+  base::Time last_on_demand_expiration_threshold_;
+
   // List of all distinct types of readers. This list is used to populate the
   // work queue.
   ExpiringVisitsReaders readers_;
 
   // Work queue for periodic expiration tasks, used by DoExpireIteration() to
   // determine what to do at an iteration, as well as populate it for future
   // iterations.
   std::queue<const ExpiringVisitsReader*> work_queue_;
 
   // Readers for various types of visits.
@@ skipping 10 matching lines @@
   // Used to generate runnable methods to do timers on this class. They will be
   // automatically canceled when this class is deleted.
   base::WeakPtrFactory<ExpireHistoryBackend> weak_factory_;
 
   DISALLOW_COPY_AND_ASSIGN(ExpireHistoryBackend);
 };
 
 }  // namespace history
 
 #endif  // COMPONENTS_HISTORY_CORE_BROWSER_EXPIRE_HISTORY_BACKEND_H_