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

content/browser/indexed_db/leveldb/leveldb_transaction.cc

 // Copyright (c) 2013 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 "content/browser/indexed_db/leveldb/leveldb_transaction.h"
 
 #include "base/logging.h"
 #include "base/memory/ptr_util.h"
 #include "base/metrics/histogram_macros.h"
 #include "base/time/time.h"
@@ skipping 345 matching lines @@
     RefreshDataIterator();
   return current_->Key();
 }
 
 StringPiece LevelDBTransaction::TransactionIterator::Value() const {
   DCHECK(IsValid());
   if (data_changed_)
     RefreshDataIterator();
   return current_->Value();
 }
+bool LevelDBTransaction::TransactionIterator::IsDetached() const {
+  return db_iterator_->IsDetached();
+}
 
 void LevelDBTransaction::TransactionIterator::DataChanged() {
   data_changed_ = true;
 }
 
 void LevelDBTransaction::TransactionIterator::Delete() {
   DCHECK(IsValid());
   if (current_ == data_iterator_.get()) {
     data_iterator_->Delete();
   } else {
@@ skipping 160 matching lines @@
 
   leveldb::Status s = db_->Write(*write_batch_);
   if (s.ok()) {
     finished_ = true;
     write_batch_->Clear();
   }
   return s;
 }
 
 }  // namespace content