Skip the creation/sync step on the bot.

tools/prepare-bisect-perf-regression.py

 #!/usr/bin/env python
 # Copyright (c) 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.
 
 """Prepare Performance Test Bisect Tool
 
 This script is used by a trybot to create a working directory and sync an
 initial copy of the depot for use in bisecting performance regressions.
 
@@ skipping 39 matching lines @@
                     'other than "chromium", you must be properly set up to '
                     'build that platform.')
   (opts, args) = parser.parse_args()
 
   if not opts.working_directory:
     print 'Error: missing required parameter: --working_directory'
     print
     parser.print_help()
     return 1
 
-  return bisect_utils.CreateBisectDirectoryAndSetupDepot(
-             opts,
-             bisect_utils.DEFAULT_GCLIENT_CUSTOM_DEPS)
+  if not bisect_utils.CheckIfBisectDepotExists(opts):
+    return bisect_utils.CreateBisectDirectoryAndSetupDepot(
+               opts,
+               bisect_utils.DEFAULT_GCLIENT_CUSTOM_DEPS)
+  return 0
 
 
 if __name__ == '__main__':
   sys.exit(main())