add PRESUBMIT for native_client_sdk.

native_client_sdk/src/build_tools/sdk_tools/sdk_update.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.
 
-import os
-import re
-import subprocess
-from sdk_update_common import *
-import sys
-import tempfile
-
 """Shim script for the SDK updater, to allow automatic updating.
 
 The purpose of this script is to be a shim which automatically updates
 sdk_tools (the bundle containing the updater scripts) whenever this script is
 run.
 
 When the sdk_tools bundle has been updated to the most recent version, this
 script forwards its arguments to sdk_updater_main.py.
 """
 
+import os
+import subprocess
+from sdk_update_common import *
+import sys
+import tempfile
+
 
 SCRIPT_DIR = os.path.dirname(os.path.abspath(__file__))
 SDK_UPDATE_MAIN = os.path.join(SCRIPT_DIR, 'sdk_update_main.py')
 SDK_ROOT_DIR = os.path.dirname(SCRIPT_DIR)
 NACLSDK_SHELL_SCRIPT = os.path.join(SDK_ROOT_DIR, 'naclsdk')
 if sys.platform.startswith('win'):
   NACLSDK_SHELL_SCRIPT += '.bat'
 SDK_TOOLS_DIR = os.path.join(SDK_ROOT_DIR, 'sdk_tools')
 SDK_TOOLS_UPDATE_DIR = os.path.join(SDK_ROOT_DIR, 'sdk_tools_update')
 
@@ skipping 69 matching lines @@
     RenameSdkToolsDirectory()
     # Call the shell script, just in case this script was updated in the next
     # version of sdk_tools
     return subprocess.call([NACLSDK_SHELL_SCRIPT] + args)
   else:
     return subprocess.call(MakeSdkUpdateMainCmd(args))
     
 
 if __name__ == '__main__':
   sys.exit(main())