move plaintext/json from global to class scope

hhvm/json.php

@@ -1,7 +1,7 @@
 <?php
 //
 // 1. JSON Test
-//
-$data = json_encode(array('message' => 'Hello, World!'));
-header('Content-Type: application/json');
-echo $data;
+require_once dirname(__FILE__).'/once.php.inc';
+
+$b = new Benchmark();
+$b->bench_json();

hhvm/once.php.inc

@@ -11,6 +11,18 @@ class Benchmark {
         ));
     }
 
+    public function bench_json()
+    {
+        header('Content-Type: application/json');
+        echo json_encode(array('message' => 'Hello, World!'));
+    }
+
+    public function bench_plaintext()
+    {
+        header('Content-Type: text/plain; charset=utf-8');
+        echo 'Hello, World!';
+    }
+
     public function bench_db()
     {
         $this->setup_db();

hhvm/plaintext.php

@@ -1,6 +1,7 @@
 <?php
 //
 // 6. Plaintext Test
-//
-header('Content-Type: text/plain; charset=utf-8');
-echo 'Hello, World!';
+require_once dirname(__FILE__).'/once.php.inc';
+
+$b = new Benchmark();
+$b->bench_plaintext();