Pass handle of the native view window to the native messaging host.

chrome/test/data/native_messaging/native_hosts/echo.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.
 
 # A simple native client in python.
 # All this client does is echo the text it receives back at the extension.
 
 import os
 import sys
 import struct
 
 def WriteMessage(message):
   try:
     sys.stdout.write(struct.pack("I", len(message)))
     sys.stdout.write(message)
     sys.stdout.flush()
     return True
   except IOError:
     return False
 
 def Main():
   message_number = 0
 
   if len(sys.argv) < 2:
     sys.stderr.write("URL of the calling application is not specified.\n")
     return;
-  caller_url = sys.argv[1]
+  for arg in sys.argv[1:]:
+    if not arg.startswith('--'):
+      caller_url = arg
+      break
 
   while 1:
     # Read the message type (first 4 bytes).
     text_length_bytes = sys.stdin.read(4)
 
     if len(text_length_bytes) == 0:
       break
 
     # Read the message length (4 bytes).
     text_length = struct.unpack('i', text_length_bytes)[0]
@@ skipping 21 matching lines @@
 
     message_number += 1
 
     if not WriteMessage(
         '{{"id": {0}, "echo": {1}, "caller_url": "{2}"}}'.format(
           message_number, text, caller_url).encode('utf-8')):
       break
 
 if __name__ == '__main__':
   Main()