mojo leveldb: Add support to use in memory database.

components/leveldb/leveldb_service_impl.h

Index: components/leveldb/leveldb_service_impl.h
diff --git a/components/leveldb/leveldb_service_impl.h b/components/leveldb/leveldb_service_impl.h
index 8d554f70ee2577146b8699c333e953d6d5a7dcff..b5f90006813eded6b2cba750a6cc9f1a5572677c 100644
--- a/components/leveldb/leveldb_service_impl.h
+++ b/components/leveldb/leveldb_service_impl.h
@@ -23,6 +23,8 @@ class LevelDBServiceImpl : public LevelDBService {
             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