here is comments from Yasumasa(reviewer):

```
This proposal mostly looks good to me, but it is better if async support is implement in higher level class.
LogFileOutput class inherited as following, and you modified LogFileOutput now (you might change LogFileStreamOutput later)

    LogOutput
        LogFileStreamOutput
            LogFileOutput

I want to add async support to LogFileStreamOutput or LogFileStreamOutput because it helps us if we add other UL output (e.g. network socket) in future.
```
https://github.com/openjdk/jdk/pull/3135#issuecomment-809977841

I would like to hoist async logging check from LogFileOutput to LogFileStreamOutput, which will include both stdout and stderr.