Add simplejson 2.1.0 and use it when it's not already installed.

presubmit_support.py

 #!/usr/bin/python
 # Copyright (c) 2006-2009 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.
 
 """Enables directory-specific presubmit checks to run at upload and/or commit.
 """
 
 __version__ = '1.3.4'
 
@@ skipping 16 matching lines @@
 import subprocess  # Exposed through the API.
 import sys  # Parts exposed through API.
 import tempfile  # Exposed through the API.
 import time
 import traceback  # Exposed through the API.
 import types
 import unittest  # Exposed through the API.
 import urllib2  # Exposed through the API.
 import warnings
 
-# json may not be available.
 try:
   import simplejson as json
 except ImportError:
   try:
     import json
   except ImportError:
-    json = None
+    # Import the one included in depot_tools.
+    import third_party.simplejson as json
 
 # Local imports.
 import gcl
 import gclient_utils
 import presubmit_canned_checks
 import scm
 
 
 # Ask for feedback only once in program lifetime.
 _ASKED_FOR_FEEDBACK = False
@@ skipping 1004 matching lines @@
                                options.commit,
                                options.verbose,
                                sys.stdout,
                                sys.stdin,
                                options.default_presubmit,
                                options.may_prompt)
 
 
 if __name__ == '__main__':
   sys.exit(Main(sys.argv))