benchmark: add --expose_internals switch

Adds --expose_internals switch to benchmark runner. This makes
misc/freelist.js benchmark run properly

Reviewed-By: James M Snell <jasnell@gmail.com>
Reviewed-By: Andreas Madsen <amwebdk@gmail.com>
PR-URL: https://github.com/nodejs/node/pull/8547

benchmark/common.js

@@ -137,7 +137,8 @@ Benchmark.prototype._run = function() {
     }
 
     const child = child_process.fork(require.main.filename, childArgs, {
-      env: childEnv
+      env: childEnv,
+      execArgv: ['--expose_internals'].concat(process.execArgv)
     });
     child.on('message', sendResult);
     child.on('close', function(code) {

benchmark/misc/freelist.js

@@ -1,13 +1,16 @@
 'use strict';
 
 var common = require('../common.js');
-var FreeList = require('internal/freelist').FreeList;
 
 var bench = common.createBenchmark(main, {
   n: [100000]
 });
 
 function main(conf) {
+  // Using internal/freelist requires node to be run with --expose_internals
+  // switch. common.js will do that when calling main(), so we require
+  // this module here
+  const FreeList = require('internal/freelist').FreeList;
   var n = conf.n;
   var poolSize = 1000;
   var list = new FreeList('test', poolSize, Object);