benchmark: add benchmark for url.format()

PR-URL: https://github.com/nodejs/node/pull/7250
Reviewed-By: Brian White <mscdex@mscdex.net>

benchmark/url/url-format.js

@@ -0,0 +1,33 @@
+'use strict';
+const common = require('../common.js');
+const url = require('url');
+const v8 = require('v8');
+
+const bench = common.createBenchmark(main, {
+  type: 'one two'.split(' '),
+  n: [25e6]
+});
+
+function main(conf) {
+  const type = conf.type;
+  const n = conf.n | 0;
+
+  const inputs = {
+    one: {slashes: true, host: 'localhost'},
+    two: {protocol: 'file:', pathname: '/foo'},
+  };
+  const input = inputs[type] || '';
+
+  // Force-optimize url.format() so that the benchmark doesn't get
+  // disrupted by the optimizer kicking in halfway through.
+  for (const name in inputs)
+    url.format(inputs[name]);
+
+  v8.setFlagsFromString('--allow_natives_syntax');
+  eval('%OptimizeFunctionOnNextCall(url.format)');
+
+  bench.start();
+  for (var i = 0; i < n; i += 1)
+    url.format(input);
+  bench.end(n);
+}