Docserver: Make MockFileSystem not iterate over the entire file system as part

chrome/common/extensions/docs/server2/chained_compiled_file_system_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.
 
 import unittest
 
 from chained_compiled_file_system import ChainedCompiledFileSystem
 from compiled_file_system import CompiledFileSystem
 from object_store_creator import ObjectStoreCreator
@@ skipping 40 matching lines @@
                      'new file in dir')
     self._new_file_system.IncrementStat('a.txt')
     self.assertNotEqual(self._chained_compiled_fs.GetFromFile('a.txt').Get(),
                         self._base_compiled_fs.GetFromFile('a.txt').Get())
     self.assertEqual(self._chained_compiled_fs.GetFromFile('a.txt').Get(),
                      self._new_file_system.ReadSingle('a.txt').Get())
 
   def testGetFromFileListing(self):
     self.assertEqual(self._chained_compiled_fs.GetFromFile('dir/').Get(),
                      self._base_compiled_fs.GetFromFile('dir/').Get())
-    self._new_file_system.IncrementStat('dir/')
+    self._new_file_system.IncrementStat('dir/new.txt')
     self.assertNotEqual(
         self._chained_compiled_fs.GetFromFileListing('dir/').Get(),
         self._base_compiled_fs.GetFromFileListing('dir/').Get())
     self.assertEqual(
         self._chained_compiled_fs.GetFromFileListing('dir/').Get(),
         self._new_file_system.ReadSingle('dir/').Get())
 
 if __name__ == '__main__':
   unittest.main()