Starts a chunked conversion.
The returned sink serves as input for the long-running conversion. The
given sink serves as output.
Source
StringConversionSink startChunkedConversion(Sink<String> sink) {
if (sink is! StringConversionSink) {
sink = new StringConversionSink.from(sink);
}
return new _LineSplitterSink(sink);
}