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/double_end/app.js

@@ -1,6 +1,5 @@
 #!/usr/bin/env node
 
 require('unit-http').createServer(function (req, res) {
-    res.end();
-    res.end();
+    res.end().end();
 }).listen(7080);