Expose ability to download network service impl in SDK.

mojo/public/tools/download_shell_binary.py

 #!/usr/bin/env python
 # Copyright 2014 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 subprocess
 import sys
 import tempfile
 import zipfile
 
 BINARY_FOR_PLATFORM = {
     "linux-x64" : "mojo_shell",
     "android-arm" : "MojoShell.apk"
 }
 
 if not sys.platform.startswith("linux"):
   print "Not supported for your platform"
   sys.exit(0)
 
 CURRENT_PATH = os.path.dirname(os.path.realpath(__file__))
-PREBUILT_FILE_PATH = os.path.join(CURRENT_PATH, "prebuilt")
+PREBUILT_FILE_PATH = os.path.join(CURRENT_PATH, "prebuilt", "shell")
 
 
 def download(tools_directory):
   stamp_path = os.path.join(PREBUILT_FILE_PATH, "VERSION")
 
   version_path = os.path.join(CURRENT_PATH, "../VERSION")
   with open(version_path) as version_file:
     version = version_file.read().strip()
 
   try:
@@ skipping 42 matching lines @@
            "cp",
            gs_path,
            temp_zip_file.name],
           stderr=subprocess.STDOUT,
           env=env)
     except subprocess.CalledProcessError as e:
       print e.output
       sys.exit(1)
 
     binary_name = BINARY_FOR_PLATFORM[platform]
+    output_dir = os.path.join(PREBUILT_FILE_PATH, platform)
     with zipfile.ZipFile(temp_zip_file.name) as z:
       zi = z.getinfo(binary_name)
       mode = zi.external_attr >> 16
-      z.extract(zi, PREBUILT_FILE_PATH)
-      os.chmod(os.path.join(PREBUILT_FILE_PATH, binary_name), mode)
+      z.extract(zi, output_dir)
+      os.chmod(os.path.join(output_dir, binary_name), mode)
 
 
 def main():
   parser = argparse.ArgumentParser(description="Download mojo_shell binaries "
                                    "from google storage")
   parser.add_argument("--tools-directory",
                       dest="tools_directory",
                       metavar="<tools-directory>",
                       type=str,
                       help="Path to the directory containing"
                            " find_depot_tools.py, specified as a relative path"
                            " from the location of this file.")
   args = parser.parse_args()
   if not args.tools_directory:
     print "Must specify --tools_directory; please see help message."
     sys.exit(1)
   return download(args.tools_directory)
 
 if __name__ == "__main__":
   sys.exit(main())