Fix `git cl format` for dart code.

git_cl.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.
 
 # Copyright (C) 2008 Evan Martin <martine@danga.com>
 
 """A git-command for integrating reviews on Rietveld."""
 
 from distutils.version import LooseVersion
@@ skipping 3816 matching lines @@
 
   # Dart's formatter does not have the nice property of only operating on
   # modified chunks, so hard code full.
   if dart_diff_files:
     try:
       command = [dart_format.FindDartFmtToolInChromiumTree()]
       if not opts.dry_run and not opts.diff:
         command.append('-w')
       command.extend(dart_diff_files)
 
-      stdout = RunCommand(command, cwd=top_dir, env=env)
+      stdout = RunCommand(command, cwd=top_dir)
       if opts.dry_run and stdout:
         return_value = 2
     except dart_format.NotFoundError as e:
       print ('Warning: Unable to check Dart code formatting. Dart SDK not ' +
              'found in this checkout. Files in other languages are still ' +
              'formatted.')
 
   # Format GN build files. Always run on full build files for canonical form.
   if gn_diff_files:
     cmd = ['gn', 'format']
@@ skipping 103 matching lines @@
 if __name__ == '__main__':
   # These affect sys.stdout so do it outside of main() to simplify mocks in
   # unit testing.
   fix_encoding.fix_encoding()
   colorama.init()
   try:
     sys.exit(main(sys.argv[1:]))
   except KeyboardInterrupt:
     sys.stderr.write('interrupted\n')
     sys.exit(1)