[chromedriver] Implement SwitchToFrame command.

chrome/test/chromedriver/chromedriver.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.
 
 import ctypes
 import json
 
 class ChromeDriverException(Exception):
   pass
 class UnknownCommand(ChromeDriverException):
@@ skipping 57 matching lines @@
   def _ExecuteSessionCommand(self, name, params={}):
     return self._ExecuteCommand(name, params, self._session_id)['value']
 
   def Load(self, url):
     self._ExecuteSessionCommand('get', {'url': url})
 
   def ExecuteScript(self, script, *args):
     return self._ExecuteSessionCommand(
          'executeScript', {'script': script, 'args': args})
 
+  def SwitchToFrame(self, id_or_name):
+    self._ExecuteSessionCommand('switchToFrame', {'id': id_or_name})
+
+  def SwitchToFrameByIndex(self, index):
+    self.SwitchToFrame(index)
+
+  def SwitchToMainFrame(self):
+    self.SwitchToFrame(None)
+
   def Quit(self):
     """Quits the browser and ends the session."""
     self._ExecuteSessionCommand('quit')