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;