mojo leveldb: Add support to use in memory database.

components/leveldb/public/interfaces/leveldb.mojom

 // Copyright 2015 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.
 
 module leveldb;
 
 import "components/filesystem/public/interfaces/directory.mojom";
 
 enum DatabaseError {
   OK,
@@ skipping 14 matching lines @@
   array<uint8> key;
   array<uint8>? value;
 };
 
 // Service which hands out databases.
 interface LevelDBService {
   // TODO(erg): What options do we want to export? All? None?
   Open(filesystem.Directory directory,
        string dbname,
        LevelDBDatabase& database) => (DatabaseError status);
+
+  OpenInMemory(LevelDBDatabase& database) => (DatabaseError status);
 };
 
 // A leveldb database.
 interface LevelDBDatabase {
   // Basic Interface -------------------------------------------------------
 
   // Sets the database entry for "key" to "value". Returns OK on success.
   Put(array<uint8> key, array<uint8> value) => (DatabaseError status);
 
   // Remove the database entry (if any) for "key".  Returns OK on
@@ skipping 12 matching lines @@
   GetSnapshot() => (uint64 snapshot_id);
 
   // Releases a previously acquired snapshot.
   ReleaseSnapshot(uint64 snapshot_id);
 
   // If |key| exists at the time |snapshot_id| was taken, return OK and the
   // value. Otherwise return NOT_FOUND.
   GetFromSnapshot(uint64 snapshot_id, array<uint8> key)
       => (DatabaseError status, array<uint8> value);
 };