Creates a new instance combining a StringSink sink and a callback
onClose which is invoked when the returned instance is closed.
Source
factory ClosableStringSink.fromStringSink(StringSink sink, void onClose())
= _ClosableStringSink;
Creates a new instance combining a StringSink sink and a callback
onClose which is invoked when the returned instance is closed.
factory ClosableStringSink.fromStringSink(StringSink sink, void onClose())
= _ClosableStringSink;