[IndexedDB] Pool and evict leveldb iterators, to save memory

content/browser/indexed_db/indexed_db_class_factory.h

 // Copyright 2014 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 CONTENT_BROWSER_INDEXED_DB_INDEXED_DB_CLASS_FACTORY_H_
 #define CONTENT_BROWSER_INDEXED_DB_INDEXED_DB_CLASS_FACTORY_H_
 
 #include <stdint.h>
 
 #include <memory>
 #include <set>
 
 #include "base/lazy_instance.h"
 #include "base/memory/ref_counted.h"
 #include "content/browser/indexed_db/indexed_db_backing_store.h"
 #include "content/browser/indexed_db/indexed_db_database.h"
 #include "content/common/content_export.h"
 #include "third_party/WebKit/public/platform/modules/indexeddb/WebIDBTypes.h"
 
 namespace leveldb {
 class Iterator;
+class Snapshot;
 }  // namespace leveldb
 
 namespace content {
 
 class IndexedDBBackingStore;
 class IndexedDBConnection;
 class IndexedDBFactory;
 class IndexedDBTransaction;
 class LevelDBDatabase;
 class LevelDBIteratorImpl;
@@ skipping 16 matching lines @@
       const IndexedDBDatabase::Identifier& unique_identifier);
 
   virtual std::unique_ptr<IndexedDBTransaction> CreateIndexedDBTransaction(
       int64_t id,
       IndexedDBConnection* connection,
       const std::set<int64_t>& scope,
       blink::WebIDBTransactionMode mode,
       IndexedDBBackingStore::Transaction* backing_store_transaction);
 
   virtual std::unique_ptr<LevelDBIteratorImpl> CreateIteratorImpl(
-      std::unique_ptr<leveldb::Iterator> iterator);
+      std::unique_ptr<leveldb::Iterator> iterator,
+      LevelDBDatabase* db,
+      const leveldb::Snapshot* snapshot);
 
   virtual scoped_refptr<LevelDBTransaction> CreateLevelDBTransaction(
       LevelDBDatabase* db);
 
  protected:
   IndexedDBClassFactory() {}
   virtual ~IndexedDBClassFactory() {}
   friend struct base::LazyInstanceTraitsBase<IndexedDBClassFactory>;
 };
 
 }  // namespace content
 
 #endif  // CONTENT_BROWSER_INDEXED_DB_INDEXED_DB_CLASS_FACTORY_H_