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

content/browser/indexed_db/leveldb/leveldb_transaction.h

 // 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.
 
 #ifndef CONTENT_BROWSER_INDEXED_DB_LEVELDB_LEVELDB_TRANSACTION_H_
 #define CONTENT_BROWSER_INDEXED_DB_LEVELDB_LEVELDB_TRANSACTION_H_
 
 #include <map>
 #include <memory>
 #include <set>
 #include <string>
 
 #include "base/gtest_prod_util.h"
 #include "base/macros.h"
 #include "base/memory/ref_counted.h"
 #include "base/strings/string_piece.h"
 #include "content/browser/indexed_db/leveldb/leveldb_comparator.h"
 #include "content/browser/indexed_db/leveldb/leveldb_database.h"
 #include "content/browser/indexed_db/leveldb/leveldb_iterator.h"
 
 namespace content {
-
-class LevelDBTransactionRangeTest;
 class LevelDBWriteBatch;
 
 class CONTENT_EXPORT LevelDBTransaction
     : public base::RefCounted<LevelDBTransaction> {
  public:
   void Put(const base::StringPiece& key, std::string* value);
 
   void Remove(const base::StringPiece& key);
 
   leveldb::Status RemoveRange(const base::StringPiece& begin,
                               const base::StringPiece& end,
                               bool upper_open);
 
   virtual leveldb::Status Get(const base::StringPiece& key,
                               std::string* value,
                               bool* found);
   virtual leveldb::Status Commit();
   void Rollback();
 
   std::unique_ptr<LevelDBIterator> CreateIterator();
 
  protected:
   virtual ~LevelDBTransaction();
   explicit LevelDBTransaction(LevelDBDatabase* db);
   friend class IndexedDBClassFactory;
 
  private:
   friend class base::RefCounted<LevelDBTransaction>;
-  friend class content::LevelDBTransactionRangeTest;
+  friend class LevelDBTransactionRangeTest;
+  friend class LevelDBTransactionTest;
   FRIEND_TEST_ALL_PREFIXES(LevelDBTransactionTest, GetAndPut);
   FRIEND_TEST_ALL_PREFIXES(LevelDBTransactionTest, Commit);
   FRIEND_TEST_ALL_PREFIXES(LevelDBTransactionTest, Iterator);
 
   struct Record {
     Record();
     ~Record();
     std::string key;
     std::string value;
     bool deleted = false;
@@ skipping 53 matching lines @@
     static std::unique_ptr<TransactionIterator> Create(
         scoped_refptr<LevelDBTransaction> transaction);
 
     bool IsValid() const override;
     leveldb::Status SeekToLast() override;
     leveldb::Status Seek(const base::StringPiece& target) override;
     leveldb::Status Next() override;
     leveldb::Status Prev() override;
     base::StringPiece Key() const override;
     base::StringPiece Value() const override;
+    // Exposed for testing.
+    bool IsDetached() const override;
     void DataChanged();
 
     // Mark the current record as deleted. If an existing record
     // is present in the uncommitted data this will convert it to
     // a deletion record, otherwise it will insert a new one.
     void Delete();
 
    private:
     enum Direction { FORWARD, REVERSE };
 
@@ skipping 53 matching lines @@
   LevelDBDatabase* db_;
   std::unique_ptr<LevelDBWriteBatch> write_batch_;
   bool finished_ = false;
 
   DISALLOW_COPY_AND_ASSIGN(LevelDBDirectTransaction);
 };
 
 }  // namespace content
 
 #endif  // CONTENT_BROWSER_INDEXED_DB_LEVELDB_LEVELDB_TRANSACTION_H_