mojo leveldb: Add support to use in memory database.

components/leveldb/leveldb_service_impl.h

 // Copyright 2016 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 COMPONENTS_LEVELDB_LEVELDB_SERVICE_IMPL_H_
 #define COMPONENTS_LEVELDB_LEVELDB_SERVICE_IMPL_H_
 
 #include "base/memory/ref_counted.h"
 #include "components/leveldb/leveldb_file_thread.h"
 #include "components/leveldb/public/interfaces/leveldb.mojom.h"
 #include "mojo/public/cpp/bindings/binding_set.h"
 
 namespace leveldb {
 
 // Creates LevelDBDatabases based scoped to a |directory|/|dbname|.
 class LevelDBServiceImpl : public LevelDBService {
  public:
   LevelDBServiceImpl();
   ~LevelDBServiceImpl() override;
 
   // Overridden from LevelDBService:
   void Open(filesystem::DirectoryPtr directory,
             const mojo::String& dbname,
             leveldb::LevelDBDatabaseRequest database,
             const OpenCallback& callback) override;
+  void OpenInMemory(leveldb::LevelDBDatabaseRequest database,
+                    const OpenInMemoryCallback& callback) override;
 
  private:
   // Thread to own the mojo message pipe. Because leveldb spawns multiple
   // threads that want to call file stuff, we create a dedicated thread to send
   // and receive mojo message calls.
   scoped_refptr<LevelDBFileThread> thread_;
 
   DISALLOW_COPY_AND_ASSIGN(LevelDBServiceImpl);
 };
 
 }  // namespace leveldb
 
 #endif  // COMPONENTS_LEVELDB_LEVELDB_SERVICE_IMPL_H_