Remove unused PATCH_TOOL and resulting dead code from bot_update.

tests/bot_update_coverage_test.py

 #!/usr/bin/env python
 # Copyright (c) 2015 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 codecs
 import copy
 import json
 import os
 import sys
@@ skipping 19 matching lines @@
     'patch_root': None,
     'issue': None,
     'patchset': None,
     'rietveld_server': None,
     'gerrit_repo': None,
     'gerrit_ref': None,
     'gerrit_rebase_patch_ref': None,
     'revision_mapping': {},
     'apply_issue_email_file': None,
     'apply_issue_key_file': None,
-    'gyp_env': None,
     'shallow': False,
-    'runhooks': False,
     'refs': [],
     'git_cache_dir': '',
     'gerrit_reset': None,
 }
 
 
 class MockedPopen(object):
   """A fake instance of a called subprocess.
 
   This is meant to be used in conjunction with MockedCall.
@@ skipping 139 matching lines @@
     return self.call.records
 
   def testBasicShallow(self):
     self.params['shallow'] = True
     bot_update.ensure_checkout(**self.params)
     return self.call.records
 
 
 if __name__ == '__main__':
   unittest.main()