[chromedriver] Implement SwitchToFrame command.

chrome/test/chromedriver/chrome.h

 // 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.
 
 #ifndef CHROME_TEST_CHROMEDRIVER_CHROME_H_
 #define CHROME_TEST_CHROMEDRIVER_CHROME_H_
 
 #include <string>
 
 #include "base/memory/scoped_ptr.h"
 
 namespace base {
 class ListValue;
 class Value;
 }
 
 class Status;
 
 class Chrome {
  public:
   virtual ~Chrome() {}
 
   virtual Status Load(const std::string& url) = 0;
-  virtual Status EvaluateScript(const std::string& expression,
+  virtual Status EvaluateScript(const std::string& frame,
+                                const std::string& expression,
                                 scoped_ptr<base::Value>* result) = 0;
-  virtual Status CallFunction(const std::string& function,
+  virtual Status CallFunction(const std::string& frame,
+                              const std::string& function,
                               const base::ListValue& args,
                               scoped_ptr<base::Value>* result) = 0;
+  virtual Status GetFrameByFunction(const std::string& frame,
+                                    const std::string& function,
+                                    const base::ListValue& args,
+                                    std::string* out_frame) = 0;
   virtual Status Quit() = 0;
 };
 
 #endif  // CHROME_TEST_CHROMEDRIVER_CHROME_H_