Revert of ensure_goma for goma canary

scripts/slave/recipe_modules/goma/resources/ensure_goma.py

 #!/usr/bin/env python
 # Copyright 2016 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 argparse
 import os
 import shutil
 import subprocess
 import sys
@@ skipping 12 matching lines @@
   if sys.platform.startswith('linux'):
     return 'linux'
 
   return None
 
 
 def main(argv):
   parser = argparse.ArgumentParser()
   parser.add_argument('--target-dir', required=True)
   parser.add_argument('--download-from-google-storage-path', required=True)
-  parser.add_argument('--canary', action='store_true')
 
   args = parser.parse_args()
 
   config = CONFIG[get_platform()]
 
   client_dir = args.target_dir
   if not os.path.exists(client_dir):
     os.makedirs(client_dir)
 
   current_repo = subprocess.check_output(
       ['git', 'ls-remote', '--get-url'], cwd=client_dir).strip()
   if current_repo != config['repo']:
     shutil.rmtree(client_dir)
     subprocess.check_call(['git', 'clone', config['repo'], client_dir])
 
   subprocess.check_call(['git', 'fetch'], cwd=client_dir)
-  rev = config['revision']
-  if arg.canary:
-    rev = 'refs/heads/master'
   subprocess.check_call(
-      ['git', 'reset', '--hard', rev], cwd=client_dir)
+      ['git', 'reset', '--hard', config['revision']], cwd=client_dir)
 
   subprocess.check_call([sys.executable,
                          args.download_from_google_storage_path,
                          '--directory',
                          '--recursive',
                          '--bucket', 'chrome-goma',
                          client_dir])
 
   subprocess.check_call(
       [sys.executable, os.path.join(client_dir, 'fix_file_modes.py')])
 
   return 0
 
 
 if __name__ == '__main__':
   sys.exit(main(sys.argv[1:]))