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/promise_handler/app.js

@@ -6,8 +6,7 @@ require('unit-http').createServer(function (req, res) {
     res.end();
 
     if (req.headers['x-write-call']) {
-        res.writeHead(200, {'Content-Type': 'text/plain'});
-        res.write('blah');
+        res.writeHead(200, {'Content-Type': 'text/plain'}).write('blah');
     }
 
     Promise.resolve().then(() => {