[chromedriver] Implement SwitchToFrame command.

chrome/test/chromedriver/chrome.h

Index: chrome/test/chromedriver/chrome.h
diff --git a/chrome/test/chromedriver/chrome.h b/chrome/test/chromedriver/chrome.h
index c7a6e5c51550573aa2e7af9c817d1d62a954156e..38ba77524f97709c92e1f8031017c98fdcdefde6 100644
--- a/chrome/test/chromedriver/chrome.h
+++ b/chrome/test/chromedriver/chrome.h
@@ -21,11 +21,17 @@ class Chrome {
   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;
 };