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

components/history/core/browser/expire_history_backend.cc

 // 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.
 
 #include "components/history/core/browser/expire_history_backend.h"
 
 #include <stddef.h>
 
 #include <algorithm>
 #include <functional>
 #include <limits>
 
 #include "base/bind.h"
 #include "base/compiler_specific.h"
+#include "base/feature_list.h"
 #include "base/files/file_enumerator.h"
 #include "base/files/file_util.h"
 #include "base/location.h"
 #include "base/logging.h"
 #include "base/sequenced_task_runner.h"
 #include "components/history/core/browser/history_backend_client.h"
 #include "components/history/core/browser/history_backend_notifier.h"
 #include "components/history/core/browser/history_database.h"
 #include "components/history/core/browser/thumbnail_database.h"
 
@@ skipping 82 matching lines @@
 // last expiration found at least kNumExpirePerIteration and we want to check
 // again "soon."
 const int kExpirationDelaySec = 30;
 
 // The number of minutes between checking, as with kExpirationDelaySec, but
 // when we didn't find enough things to expire last time. If there was no
 // history to expire last iteration, it's likely there is nothing next
 // iteration, so we want to wait longer before checking to avoid wasting CPU.
 const int kExpirationEmptyDelayMin = 5;
 
+// Feature that enables clearing old on-demand favicons.
+const base::Feature kClearOldOnDemandFavicons{
+    "ClearOldOnDemandFavicons", base::FEATURE_DISABLED_BY_DEFAULT};
+
 }  // namespace
 
 
 // ExpireHistoryBackend::DeleteEffects ----------------------------------------
 
 ExpireHistoryBackend::DeleteEffects::DeleteEffects() {
 }
 
 ExpireHistoryBackend::DeleteEffects::~DeleteEffects() {
 }
@@ skipping 166 matching lines @@
   // For now, we explicitly add all known readers. If we come up with more
   // reader types (in case we want to expire different types of visits in
   // different ways), we can make it be populated by creator/owner of
   // ExpireHistoryBackend.
   readers_.push_back(GetAllVisitsReader());
   readers_.push_back(GetAutoSubframeVisitsReader());
 
   // Initialize the queue with all tasks for the first set of iterations.
   InitWorkQueue();
   ScheduleExpire();
+
+  // Remove favicons that are not bound to visits.
+  if (!base::FeatureList::IsEnabled(kClearOldOnDemandFavicons))
+    return;
+  task_runner_->PostDelayedTask(
+      FROM_HERE,
+      base::Bind(&ExpireHistoryBackend::ClearOldOnDemandFavicons,
+                 weak_factory_.GetWeakPtr()),
+      base::TimeDelta::FromSeconds(kExpirationDelaySec));
+}
+
+void ExpireHistoryBackend::ClearOldOnDemandFavicons() {
+  thumb_db_->ClearOldOnDemandFavicons(GetCurrentExpirationTime());
 }
 
 void ExpireHistoryBackend::DeleteFaviconsIfPossible(DeleteEffects* effects) {
   if (!thumb_db_)
     return;
 
   for (std::set<favicon_base::FaviconID>::const_iterator i =
            effects->affected_favicons.begin();
        i != effects->affected_favicons.end(); ++i) {
     if (!thumb_db_->HasMappingFor(*i)) {
@@ skipping 150 matching lines @@
       base::Bind(&ExpireHistoryBackend::DoExpireIteration,
                  weak_factory_.GetWeakPtr()),
       delay);
 }
 
 void ExpireHistoryBackend::DoExpireIteration() {
   DCHECK(!work_queue_.empty()) << "queue has to be non-empty";
 
   const ExpiringVisitsReader* reader = work_queue_.front();
   bool more_to_expire = ExpireSomeOldHistory(
       GetCurrentExpirationTime(), reader, kNumExpirePerIteration);

[pkotwicz, 2017/06/22 20:32:22]

Can we call ClearOldOnDemandFavicons() here if |more_to_expire| is false

You can make ClearOldOnDemandFavicons() return a std::vector of pairs containing
(page_url, icon_id) and check whether any of the pages are bookmarked here. This
would be consistent with how history expiry works.

You can use:
- ThumbnailDatabase::DeleteFavicon() (existing function)
and
- ThumbnailDatabase::DeleteIconMappingForFaviconId() (new function)
to do the deletion

[jkrcal, 2017/07/06 17:01:48]

Done.

 
   work_queue_.pop();
   // If there are more items to expire, add the reader back to the queue, thus
   // creating a new task for future iterations.
   if (more_to_expire)
     work_queue_.push(reader);
 
   ScheduleExpire();
 }
 
@@ skipping 21 matching lines @@
   BroadcastNotifications(&deleted_effects, DELETION_EXPIRED);
 
   return more_to_expire;
 }
 
 void ExpireHistoryBackend::ParanoidExpireHistory() {
   // TODO(brettw): Bug 1067331: write this to clean up any errors.
 }
 
 }  // namespace history