Small fix for package_management on Mac OS X.

package_management.py

 #!/usr/bin/env python
 # 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.
 
 """Package Management
 
 This module is used to bring in external Python dependencies via eggs from the
 PyPi repository.
 
@@ skipping 454 matching lines @@
   having been added to the parent process as it may cause packages to be
   added and/or removed.
 
   Returns:
     True on success, False otherwise.
   """
   if _SiteDirectoryIsUpToDate():
     return True
 
   try:
-    AddSiteDirectory(SITE_DIR)
+    EnsureSiteDirectory(SITE_DIR)
     import pkg_resources
 
     # Determine if any packages actually need installing.
     missing_packages = []
     for package in [SETUPTOOLS] + list(PACKAGES):
       pkg = Package(*package)
       req = pkg.GetAsRequirementString()
 
       # It may be that this package is already available in the site
       # directory. If so, we can skip past it without trying to install it.
@@ skipping 107 matching lines @@
     exec('result = %s' % sys.argv[1])
 
     # Translate the success state to a return code.
     return not result
   else:
     return not SetupSiteDirectory()
 
 
 if __name__ == '__main__':
   sys.exit(Main())