Docserver: achieve online vs offline (cron vs instance) behaviour at the object

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

 # Copyright (c) 2012 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 os
+import sys
 
 from file_system import FileSystem, FileNotFoundError, StatInfo, ToUnicode
 from future import Future
 
 class LocalFileSystem(FileSystem):
-  """FileSystem implementation which fetches resources from the local
+  '''FileSystem implementation which fetches resources from the local
   filesystem.
-  """
-  def __init__(self, base_path):
+  '''
+  def __init__(self, base_path=None):
+    if base_path is None:
+      # Default to the base of the extensions directory.
+      base_path = os.path.join(sys.path[0], os.pardir, os.pardir)
     self._base_path = self._ConvertToFilepath(base_path)
 
   def _ConvertToFilepath(self, path):
     return path.replace('/', os.sep)
 
   def _ReadFile(self, filename, binary):
     try:
       mode = 'rb' if binary else 'r'
       with open(os.path.join(self._base_path, filename), mode) as f:
         contents = f.read()
@@ skipping 34 matching lines @@
                       for filename in os.listdir(path))
     else:
       versions = None
     try:
       return StatInfo(os.stat(path).st_mtime, versions)
     except OSError as e:
       raise FileNotFoundError('os.stat failed for %s: %s' % (path, e))
 
   def Stat(self, path):
     return self._CreateStatInfo(os.path.join(self._base_path, path))