[chrome_remote_control] Use monkey patching for stubs.

tools/chrome_remote_control/chrome_remote_control/desktop_browser_finder.py

 # 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.
 """Finds desktop browsers that can be controlled by chrome_remote_control."""
 
 import logging
-import os as real_os
-import sys as real_sys
-import subprocess as real_subprocess
+import os
+import subprocess
+import sys
 
 from chrome_remote_control import browser
 from chrome_remote_control import desktop_browser_backend
 from chrome_remote_control import possible_browser
 
 ALL_BROWSER_TYPES = ','.join([
     'exact',
     'release',
     'debug',
     'canary',
@@ skipping 10 matching lines @@
     self._is_content_shell = is_content_shell
 
   def __repr__(self):
     return 'PossibleDesktopBrowser(browser_type=%s)' % self.browser_type
 
   def Create(self):
     backend = desktop_browser_backend.DesktopBrowserBackend(
         self._options, self._local_executable, self._is_content_shell)
     return browser.Browser(backend)
 
-def FindAllAvailableBrowsers(options,
-                             os = real_os,
-                             sys = real_sys,
-                             subprocess = real_subprocess):
+def FindAllAvailableBrowsers(options):
   """Finds all the desktop browsers available on this machine."""
   browsers = []
 
   has_display = True
   if (sys.platform.startswith('linux') and
       os.getenv('DISPLAY') == None):
     has_display = False
 
   # Add the explicit browser executable if given.
   if options.browser_executable:
@@ skipping 46 matching lines @@
 
     if os.path.exists(mac_system):
       browsers.append(PossibleDesktopBrowser('system', options,
                                              mac_system, False))
 
   # Linux specific options.
   if sys.platform.startswith('linux'):
     # Look for a google-chrome instance.
     found = False
     try:
-      with open(real_os.devnull, 'w') as devnull:
+      with open(os.devnull, 'w') as devnull:
         found = subprocess.call(['google-chrome', '--version'],
                                 stdout=devnull, stderr=devnull) == 0
     except OSError:
       pass
     if found:
       browsers.append(
           PossibleDesktopBrowser('system', options,
                                  'google-chrome', False))
 
   # Win32-specific options.
@@ skipping 10 matching lines @@
     if os.path.exists(win_system):
       browsers.append(PossibleDesktopBrowser('system', options,
                                              win_system, False))
 
   if len(browsers) and not has_display:
     logging.warning('Found (%s), but you have a DISPLAY environment set.' %
                     ','.join([b.browser_type for b in browsers]))
     return []
 
   return browsers