Correct $ref links in extensions documentation server relative location.

chrome/common/extensions/docs/server2/intro_data_source_test.py

 #!/usr/bin/env python
 # Copyright 2013 The Chromium Authors. All rights reserved.
 # Use of this source code is governed by a BSD-style license that can be
 # found in the LICENSE file.
 
 from intro_data_source import IntroDataSource
 from server_instance import ServerInstance
+from servlet import Request
 from test_data.canned_data import CANNED_TEST_FILE_SYSTEM_DATA
 from test_file_system import TestFileSystem
 import unittest
 
 class IntroDataSourceTest(unittest.TestCase):
   def setUp(self):
     self._server_instance = ServerInstance.ForTest(
         TestFileSystem(CANNED_TEST_FILE_SYSTEM_DATA))
 
   def testIntro(self):
-    intro_data_source = IntroDataSource(self._server_instance, None)
+    intro_data_source = IntroDataSource(
+        self._server_instance, Request.ForTest(''))
     intro_data = intro_data_source.get('test_intro')
     article_data = intro_data_source.get('test_article')
 
     expected_intro = 'you<h2>first</h2><h3>inner</h3><h2>second</h2>'
     # Article still has the header.
     expected_article = '<h1>hi</h1>' + expected_intro
 
     self.assertEqual(expected_intro, intro_data.Render().text)
     self.assertEqual(expected_article, article_data.Render().text)
 
 
 if __name__ == '__main__':
   unittest.main()