[chromedriver] Implement SwitchToFrame command.

chrome/test/chromedriver/chromedriver.py

Index: chrome/test/chromedriver/chromedriver.py
diff --git a/chrome/test/chromedriver/chromedriver.py b/chrome/test/chromedriver/chromedriver.py
index acb644581bc33600532b7f0f5d167a99e950ebb3..97793e86f550b13482bebcc127fd5478baf5c2ce 100644
--- a/chrome/test/chromedriver/chromedriver.py
+++ b/chrome/test/chromedriver/chromedriver.py
@@ -75,6 +75,15 @@ class ChromeDriver(object):
     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')