Node.js: returning "this" from writeHead() to allow chaining.

In Node.js version 11.10.0 and later, the writeHead() function returns "this".

test/node/mirror/app.js

@@ -6,7 +6,7 @@ require('unit-http').createServer(function (req, res) {
         body += chunk.toString();
     });
     req.on('end', () => {
-        res.writeHead(200, {'Content-Length': Buffer.byteLength(body)});
-        res.end(body);
+        res.writeHead(200, {'Content-Length': Buffer.byteLength(body)})
+           .end(body);
     });
 }).listen(7080);