mojo leveldb: Add support to use in memory database.

components/leveldb/leveldb_service_impl.cc

 // 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.
 
 #include "components/leveldb/leveldb_service_impl.h"
 
 #include "components/leveldb/env_mojo.h"
 #include "components/leveldb/leveldb_database_impl.h"
 #include "components/leveldb/util.h"
 #include "third_party/leveldatabase/env_chromium.h"
+#include "third_party/leveldatabase/src/helpers/memenv/memenv.h"
 #include "third_party/leveldatabase/src/include/leveldb/db.h"
 #include "third_party/leveldatabase/src/include/leveldb/env.h"
 #include "third_party/leveldatabase/src/include/leveldb/filter_policy.h"
 #include "third_party/leveldatabase/src/include/leveldb/slice.h"
 
 namespace leveldb {
 
 LevelDBServiceImpl::LevelDBServiceImpl() : thread_(new LevelDBFileThread) {}
 
 LevelDBServiceImpl::~LevelDBServiceImpl() {}
@@ skipping 25 matching lines @@
   leveldb::Status s = leveldb::DB::Open(options, dbname.To<std::string>(), &db);
 
   if (s.ok()) {
     new LevelDBDatabaseImpl(std::move(database), std::move(env_mojo),
                             scoped_ptr<leveldb::DB>(db));
   }
 
   callback.Run(LeveldbStatusToError(s));
 }
 
+void LevelDBServiceImpl::OpenInMemory(leveldb::LevelDBDatabaseRequest database,
+                                      const OpenCallback& callback) {
+  leveldb::Options options;
+  options.create_if_missing = true;
+  options.max_open_files = 0;  // Use minimum.
+  options.reuse_logs = leveldb_env::kDefaultLogReuseOptionValue;
+
+  scoped_ptr<leveldb::Env> env(leveldb::NewMemEnv(leveldb::Env::Default()));
+  options.env = env.get();
+
+  leveldb::DB* db = nullptr;
+  leveldb::Status s = leveldb::DB::Open(options, "", &db);
+
+  if (s.ok()) {
+    new LevelDBDatabaseImpl(std::move(database), std::move(env),
+                            scoped_ptr<leveldb::DB>(db));
+  }
+
+  callback.Run(LeveldbStatusToError(s));
+}
+
 }  // namespace leveldb