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

components/history/core/browser/expire_history_backend.cc

Index: components/history/core/browser/expire_history_backend.cc
diff --git a/components/history/core/browser/expire_history_backend.cc b/components/history/core/browser/expire_history_backend.cc
index d57a60432afb85c3f74790c13d50d8e7865dd7b9..1d36f25056f1375675a3be9a438c6035f8fa9885 100644
--- a/components/history/core/browser/expire_history_backend.cc
+++ b/components/history/core/browser/expire_history_backend.cc
@@ -12,6 +12,7 @@
 
 #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"
@@ -114,8 +115,23 @@ const int kExpirationDelaySec = 30;
 // iteration, so we want to wait longer before checking to avoid wasting CPU.
 const int kExpirationEmptyDelayMin = 5;
 
+bool IsAnyURLBookmarked(HistoryBackendClient* backend_client,
+                        const std::vector<GURL>& urls) {
+  for (const GURL& url : urls) {
+    if (backend_client->IsBookmarked(url))
+      return true;
+  }
+  return false;
+}
+
 }  // namespace
 
+namespace internal {
+
+const base::Feature kClearOldOnDemandFavicons{
+    "ClearOldOnDemandFavicons", base::FEATURE_DISABLED_BY_DEFAULT};
+
+}  // namespace internal
 
 // ExpireHistoryBackend::DeleteEffects ----------------------------------------
 
@@ -477,10 +493,37 @@ void ExpireHistoryBackend::DoExpireIteration() {
   // creating a new task for future iterations.
   if (more_to_expire)
     work_queue_.push(reader);
+  // Otherwise do a final clean-up - remove old favicons not bound to visits.
+  else
+    ClearOldOnDemandFavicons(GetCurrentExpirationTime());
 
   ScheduleExpire();
 }
 
+void ExpireHistoryBackend::ClearOldOnDemandFavicons(
+    base::Time expiration_threshold) {
+  if (!base::FeatureList::IsEnabled(internal::kClearOldOnDemandFavicons))
+    return;
+
+  std::map<favicon_base::FaviconID, IconMappingsForExpiry> favicons =
+      thumb_db_->GetOldOnDemandFavicons(expiration_threshold);
+  DeleteEffects effects;
+
+  for (auto id_and_urls_pair : favicons) {
+    favicon_base::FaviconID icon_id = id_and_urls_pair.first;
+    const IconMappingsForExpiry& urls = id_and_urls_pair.second;
+
+    if (backend_client_ && IsAnyURLBookmarked(backend_client_, urls.page_urls))
+      continue;
+
+    thumb_db_->DeleteFavicon(icon_id);
+    thumb_db_->DeleteIconMappingsForFaviconId(icon_id);
+    effects.deleted_favicons.insert(urls.icon_url);
+  }
+
+  BroadcastNotifications(&effects, DELETION_EXPIRED);
+}
+
 bool ExpireHistoryBackend::ExpireSomeOldHistory(
     base::Time end_time,
     const ExpiringVisitsReader* reader,