Adding URL endpoint for switchToParentFrame

This allows consumers of the webdriver-server module to implement the
switchToParentFrame command. Note that this does **not** mean that the
command is automatically implemented in drivers that use this module; it
simply means that the driver will correctly understand the URL endpoint.
As an example, the IE driver should now properly return "command not
implemented" rather than "unknown command".

cpp/webdriver-server/command_types.h

@@ -47,6 +47,7 @@ namespace CommandType {
   const std::string GetWindowHandles = "getWindowHandles";
   const std::string SwitchToWindow = "switchToWindow";
   const std::string SwitchToFrame = "switchToFrame";
+  const std::string SwitchToParentFrame = "switchToParentFrame";
   const std::string GetActiveElement = "getActiveElement";
   const std::string GetCurrentUrl = "getCurrentUrl";
   const std::string GetPageSource = "getPageSource";

cpp/webdriver-server/server.cc

@@ -639,6 +639,7 @@ void Server::PopulateCommandRepository() {
   this->AddCommand("/session/:sessionid/execute_async", "POST",  webdriver::CommandType::ExecuteAsyncScript);
   this->AddCommand("/session/:sessionid/screenshot", "GET",  webdriver::CommandType::Screenshot);
   this->AddCommand("/session/:sessionid/frame", "POST",  webdriver::CommandType::SwitchToFrame);
+  this->AddCommand("/session/:sessionid/frame/parent", "POST",  webdriver::CommandType::SwitchToParentFrame);
   this->AddCommand("/session/:sessionid/window", "POST",  webdriver::CommandType::SwitchToWindow);
   this->AddCommand("/session/:sessionid/window", "DELETE",  webdriver::CommandType::Close);
   this->AddCommand("/session/:sessionid/cookie", "GET",  webdriver::CommandType::GetAllCookies);