Add ability to specify gyp dir to gyp_to_android.

platform_tools/android/bin/gyp_to_android.py

 #!/usr/bin/python
 
 # Copyright 2014 Google Inc.
 #
 # Use of this source code is governed by a BSD-style license that can be
 # found in the LICENSE file.
 
 """
 Script for generating the Android framework's version of Skia from gyp
 files.
 """
 
+import argparse
 import os
 import shutil
 import sys
 import tempfile
 
 # Find the top of trunk
 SCRIPT_DIR = os.path.abspath(os.path.dirname(__file__))
 SKIA_DIR = os.path.normpath(os.path.join(SCRIPT_DIR, os.pardir, os.pardir,
                                          os.pardir))
 
@@ skipping 167 matching lines @@
     deviations_from_common.append(makefile_writer.VarsDictData(arm64_var_dict,
                                                                'arm64'))
 
     makefile_writer.write_android_mk(target_dir=target_dir,
         common=common, deviations_from_common=deviations_from_common)
 
   finally:
     shutil.rmtree(tmp_folder)
 
 if __name__ == '__main__':
-  main()
+  parser = argparse.ArgumentParser()
+  parser.add_argument('--gyp_source_dir', help='Source of gyp program. '
+                      'e.g. <path_to_skia>/third_party/externals/gyp')
+  args = parser.parse_args()
+
+  main(gyp_source_dir=args.gyp_source_dir)