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

components/history/core/browser/thumbnail_database.cc

Index: components/history/core/browser/thumbnail_database.cc
diff --git a/components/history/core/browser/thumbnail_database.cc b/components/history/core/browser/thumbnail_database.cc
index c8b430f4f71d8dd70f0111995c5ce74297cec7d9..1415b037f45f4295a175d30e06ef98435941f630 100644
--- a/components/history/core/browser/thumbnail_database.cc
+++ b/components/history/core/browser/thumbnail_database.cc
@@ -412,6 +412,31 @@ void ThumbnailDatabase::TrimMemory(bool aggressively) {
   db_.TrimMemory(aggressively);
 }
 
+std::vector<std::pair<favicon_base::FaviconID, GURL>>
+ThumbnailDatabase::GetOldOnDemandFavicons(base::Time threshold) {
+  // Select all bitmaps (and their page URLs) that have not been accessed for a
+  // while. Restrict to on-demand bitmaps (i.e. with last_requested != 0).
+  // TODO(jkrcal): In M63, remove the "(last_requested=0 AND last_updated=0)"
+  // clause which is only transitional - to clean up on demand favicons stored
+  // before this function has been implemented.
+  sql::Statement delete_candidates(db_.GetCachedStatement(
+      SQL_FROM_HERE,
+      "SELECT favicon_bitmaps.icon_id, icon_mapping.page_url FROM "
+      "favicon_bitmaps, icon_mapping WHERE favicon_bitmaps.icon_id = "
+      "icon_mapping.icon_id AND ((last_requested=0 AND last_updated=0) OR "
+      "(last_requested>0 AND last_requested<?));"));
+  delete_candidates.BindInt64(0, threshold.ToInternalValue());
+
+  std::vector<std::pair<favicon_base::FaviconID, GURL>> favicons;
+
+  while (delete_candidates.Step()) {
+    favicons.push_back(std::make_pair(delete_candidates.ColumnInt64(0),
+                                      GURL(delete_candidates.ColumnString(1))));
+  }
+
+  return favicons;
+}
+
 bool ThumbnailDatabase::GetFaviconBitmapIDSizes(
     favicon_base::FaviconID icon_id,
     std::vector<FaviconBitmapIDSize>* bitmap_id_sizes) {
@@ -778,6 +803,14 @@ bool ThumbnailDatabase::DeleteIconMappings(const GURL& page_url) {
   return statement.Run();
 }
 
+bool ThumbnailDatabase::DeleteIconMappingsForFaviconId(
+    favicon_base::FaviconID id) {
+  sql::Statement statement(db_.GetCachedStatement(
+      SQL_FROM_HERE, "DELETE FROM icon_mapping WHERE icon_id=?"));
+  statement.BindInt64(0, id);
+  return statement.Run();
+}
+
 bool ThumbnailDatabase::DeleteIconMapping(IconMappingID mapping_id) {
   sql::Statement statement(db_.GetCachedStatement(SQL_FROM_HERE,
       "DELETE FROM icon_mapping WHERE id=?"));