Catch ERROR_INVALID_WINDOW_HANDLE in the quit chrome script.

chrome/test/mini_installer/quit_chrome.py

 # Copyright 2013 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.
 
 """Quits Chrome.
 
 This script sends a WM_CLOSE message to each window of Chrome and waits until
 the process terminates.
 """
 
 import optparse
+import pywintypes
 import sys
 import time
 import win32con
 import win32gui
+import winerror
 
 import chrome_helper
 
 
 def CloseWindows(process_path):
   """Closes all windows owned by processes whose path is |process_path|.
 
   Args:
     process_path: The path to the process.
 
   Returns:
     A boolean indicating whether the processes successfully terminate within
     30 seconds.
   """
   start_time = time.time()
   while time.time() - start_time < 30:
     process_ids = chrome_helper.GetProcessIDs(process_path)
     if not process_ids:
       return True
 
     for hwnd in chrome_helper.GetWindowHandles(process_ids):
-      win32gui.PostMessage(hwnd, win32con.WM_CLOSE, 0, 0)
+      try:
+        win32gui.PostMessage(hwnd, win32con.WM_CLOSE, 0, 0)
+      except pywintypes.error as error:
+        # It's normal that some window handles have become invalid.
+        if error.args[0] != winerror.ERROR_INVALID_WINDOW_HANDLE:
+          raise
     time.sleep(0)
   return False
 
 
 def main():
   usage = 'usage: %prog chrome_path'
   parser = optparse.OptionParser(usage, description='Quit Chrome.')
   _, args = parser.parse_args()
   if len(args) != 1:
     parser.error('Incorrect number of arguments.')
   chrome_path = args[0]
 
   if not CloseWindows(chrome_path):
     raise Exception('Could not quit Chrome.')
   return 0
 
 
 if __name__ == '__main__':
   sys.exit(main())